With patch 4.0.1 in our rearview mirror, we've had over a week to fix our addons and get our houses in order. I've already had a few decent raid DPS parses forwarded to me by subtlety rogues, who are finally able to actually do reasonable DPS. Traditionally, there has always been a few "bad" specs in WoW, but subtlety was so bad that it was tier below the other bad specs. Its arrival has brought back several of my old friends from retirement, who were looking forward to the frenetic rotation of finishers.
Assassination rogues have been enjoying the synergy between Vendetta and cooldown like Bloodlust, and their relative DPS is still decent. The addition of Rupture as a finisher and Backstab as an alternate generator has their rotation shaken up a bit, but still easily manageable. I actually found the Mutilate-centric build to be pretty fun to play after the patch, and I'll be using it to raid with for the immediate future. However, it wasn't assassination's playstyle that caused me to promote it to my main spec, but rather combat's current weakness that drove me to enchant my daggers with Mongoose.