If you've got your kitty DPS rotation down pact now, and as an added bonus did well with the slightly more difficult rotation in wrath, you are in a prime position to pick up a subtlety rogue and play like a pro. They are just that similar.
In fact I have come to enjoy subtlety DPS over kitty DPS after playing my rogue more regularly; cat form comes off as a cheap imitation afterwards. More so now that most all of the tanking utility will be removed from the feral DPS spec. What utility will kitties have left? A lackluster innervate, a battle rez that two other classes provide, and some limited off healing ability which would be time better spent DPSing. Rest in peace hero bear, you will be in our hearts, always.
Back to subtlety DPS; rogues like cats like to start off in stealth, it is even more important for subtlety rogues because we get a buff called 'Master of Subtlety' buffing our damage by 10% for 6 seconds after breaking stealth. Like cats we also like to jump into combat with 'Shadowstep' which bears a striking similarity to a cat's 'Feral Charge'. Then we unleash an opener, 'Ambush', for big damage just like a cat would use 'Ravage'. More on this later, but just like a cat will also use 'Feral Charge' with the 'Stampede' talent to get off additional 'Ravage's off during combat, rogues too will use 'Shadowstep' with 'Shadow Dance' to get off additional 'Ambush'es.
Now is a good time to mention the first difference for playing your rogue. You'll want to macro 'Premeditation' and 'Pickpocket' into all of your openers: 'Cheap Shot' ('Pounce' to cats), 'Garrote' (rogues get one more opener than cats, it's a silence/bleed instead of a stun/bleed) and 'Ambush'. Neither ability triggers the global cooldown so you can have them go off invisibly behind the scenes. Be sure to have auto loot enabled so you don't have loot windows pop up at the start of combat. Optionally you could also not macro 'Pickpocket' into your openers, but I find I don't otherwise remember to 'Pickpocket' in fast paced dungeons or raids.
Once you are out of stealth it is time to start building combo points, oh wait, you already have 5. Did I mention subtlety rogues build combo points a hell of a lot faster than cats (and other rogues for that matter)? So while your cat would be applying 'Mangle', 'Faerie Fire', 'Rake' and 'Shred'ding to get some combo points, your rogue already has to pick out a finisher.
Subtlety rogues use four finishers to maintain 2 buffs ('Slice and Dice' and 'Recuperate') and one debuff ('Rupture'). Cats on the other hand only use three finishers to maintain one buff ('Savage Roar') and one debuff ('Rip'). Cats always prioritize 'Rip' over 'Savage Roar', but rogues are a little more complicated.
If you are fresh out of stealth, and have your 10% damage buff, 'Rupture' is your best choice if you will be maintaining it for a few minutes; think boss fight. Otherwise it is better to start with 'Slice and Dice', this is what you will start with on trash. If 'Slice and Dice' is already up, and your target will stay alive for 20 seconds or so for the bleed to tick a while, then you should apply 'Rupture', otherwise pop 'Recuperate'. When both your 'Slice and Dice' and 'Recuperate' don't need to be refreshed, use 'Eviscerate' to do some damage and dump your combo points. 'Eviscerate' will also refresh your 'Rupture'; much like 'Blood in the Water' cause your 'Ferocious Bite' to refresh 'Rip', but all the time. Unlike cats which will apply 'Rip' even if it will only tick a couple times, rogues will forgo their long term bleed entirely and just use 'Eviscerate' on short fights.
I suppose it is a good time to mention 'Honor Among Thieves'. Subtlety rogues not only generate extra combo points for their own crits like cats do, they also generate extra combo points for everyone else's (including healers, but more on that in a moment). Just like it is beneficial for cats to just auto attack and pool energy at times, to prepare for a 'Berserk' for example; it is doubly important for subtlety rogues to pool energy prior to gaining that 5th combo point. If we use an ability to get that last combo point ourselves we'll have wasted a combo point that would have been gained through 'Honor Among Thieves', but if we sit there a moment at four combo points we get the last combo point free and have enough energy saved up to use a finisher immediately so as to not waste the next free combo point that comes our way. Even outside of a group auto attacks and the bleed from 'Glyph of Hemorrhage' will get us that 5th combo point while pooling energy. It is a little slower, but at higher gear levels you can pull off your usual rotation solo and/or on a combat dummy.
I mentioned gaining combo points from healers earlier. You can use this to your advantage gaining combo points out of combat between or before pulls, so long as you have a mob targetted. This is a great way to get 'Slice and Dice' up before you even start attacking for maximum damage. Healers are usually tossing heals around after/before a pull so be sure to take advantage of thier crits.
Now back to generating combo points yourself, like those workaday cats do. You'll want to apply and maintain 'Hemorrhage' which when glyphed is sort of like a combination of 'Mangle' and 'Rake'. 'Hemorrhage' is also your primary combo point generator when you are forced to attack from the front, just like 'Mangle' for cats. When 'Hemorrhage' is up, and you can get behind your target, you'll use 'Backstab' to generate combo point (just up to four remember).
When if comes to DPS cooldowns subtlety rogues have four: 'Shadowstep' which really just enhances the other three, 'Shadow Dance', 'Vanish' and 'Preparation'. All these cooldown share a common goal, which is to use 'Ambush' as much as possible. 'Shadowstep' buffs the damage of your next 'Ambush' so you want to use it right before you 'Vanish'/'Ambush' or in the case of 'Shadow Dance' you want to use 'Shadowstep' after the first 'Ambush' (I'll get into details in a moment). 'Preparation' resets the cooldown on vanish allowing you to use it more often as a DPS cooldown.
Now as awe inspiring as it might be on a short fight we don't want to blow all these cooldowns in rapid succession on a long fight. Well not within the same ten seconds anyway. 'Ambush', along with our other two openers, provides an armor bypassing buff via the 'Find Weakness' talent that lasts for ten seconds. Bypassing 70% of our targets armor is quite the DPS boost. This is why when we use 'Shadow Dance' we don't buff 'Ambush' with our 'Shadowstep' ability until the second 'Ambush'. That allows us to have our empowered 'Ambush' benefit from 'Find Weakness'. Oh yeah, this is deep stuff; just imagine the possibilities of working these cooldowns into specific boss fights. There is a reason Subtlety has the highest potential damage output of any class/spec.
Let's talk about survivability and utility now. Cats have two cooldowns to reduce incoming damage: 'Survival Instincts' and 'Barkskin'. In addition to that cats have the passive healing provided by 'Leader of the Pack', and if glyphed for it 'Ferocious Bite' also provides a self heal. This is all well and good, but kitties are still gonna get tore up pretty bad.
Rogues large damage reduction cooldown 'Evasion' avoids damage rather than reducing it. We also have 'Cloak of Shadows' to remove any dots and reduce incoming magic damage or 'Combat Readiness' which reduces incoming physical damage and shares a cooldown with 'Cloak of Shadows'. These abilities only work for direct damage though. What to we rogues do about AOE damage? Laugh it off for the most part. Rogues have an ability called 'Feint' which like 'Cower' reduced aggro, but it also reduces AOE damage by 50% (this can be talented for up to 80%). So rogues have some serious staying power in AOE situations. That doesn't even include the healing provided by 'Recuperate' that keeps us pretty close to topped off while everyone else's health bars are dropping like rocks.
Speaking of AOE, subtlety rogues don't. It's not that we can't, the 'Fan of Knives' button is there; our single target rotation just does more damage. Hopefully that will change in the future, but right now subtlety does the lowest AOE damage of any class/spec. It is more laughable than shaman AOE at its worst. So as a cat coming from a 'Swipe' spamming AOE utopia, be prepared to be disappointed. Of course if there are a bazillion little mobs that dies quickly in a group it is better to AOE, but it won't happen often. Keep 'Wound Poison' on your thrown weapon just in case, it works out to more damage than 'Instant Poison' for subtlety AOE.
I suppose poisons are a new mechanic for cats. You go to the poison vendor and buy a bunch of each, but more 'Instant Poison' and 'Deadly Poison' as these will go on your mainhand and offhand daggers respectively. See how I snuck that in there, subtlety should be using daggers.
For completeness sake I will mention the last few remaining rogue abilities you should be aware of. 'Gouge' is a frontal attack which will incapacitate your target until it takes damage, bleed effects don't count if you are talented correctly into 'Sanguinary Vein'. You can probably stick this in the same spot you have 'Rake' on your cat.
A quick note on where to stick abilities, most subtlety abilities have abilities almost exactly the same as cat abilities so you should stick them in the same spots to ease your transition. I mention sticking 'Gouge' where you had 'Rake', but a couple other dissimilar abilities I stuck in the same spots are: 'Slice and Dice'/'Savage Roar' and 'Recuperate'/'Tiger's Fury.
I already mentioned 'Pounce' and 'Cheap Shot' being equivalent opening stuns; 'Kidney Shot' is the equivalent finishing stun to 'Maim'. Rogues don't have a bash like cats do flipping to bear, but 'Gouge' fills that role rather well.
Cats can remove enrage/frenzy effects with 'Soothe' which rogues can do with 'Shiv'. Cats can also use 'Remove Corruption' to remove curses which rogues would use 'Cloak of Shadows' for. These are good abilities to keep in similar places between classes.
So far as crowd control goes rogues have 'Sap' which can only be used on mobs out of combat, but when glyphed lasts for 3 minutes. If that isn't long enough rogues also have 'Blind' which will cause a mob to wander around for another full minute.
That brings us to the last couple rogue only utility abilities: 'Smoke Bomb' and 'Tricks of the Trade'. Smoke bomb isn't useful in many places, it just stops direct damage spells from hitting people inside it. Sometime it is useful, but not too often.
‘Tricks of the Trade’ on the other hand is an awesome ability, and should be used often. It behaves a lot like misdirect, but in addition to redirecting your aggro to someone else, it also provides a damage buff to whomever you "tricks" to. As you can imagine this leads to pairs of rogues "tricksing" one another throughout a fight to increase each other’s damage. Since they are just redirecting their threat to each other that portion of the ability cancels itself out. Usually you'll just "tricks" the tank to avoid pulling aggro early in the fight, but you can also use it on a DPS to boost their damage so long as the tank can maintain aggro (not so much an issue anymore).
So concludes this massive wall of text giving anyone familiar with kitty DPS a massive head start into subtlety DPS.