There's little doubt that Aperture has been harmed by being slower than Lightroom on equivalent Apple hardware - as well as by being worse than glacial on non-Apple computers. For myself, I never found version 1.56 was too bad on my MacBookPro with 2Gb RAM - slower though not impossibly so was my feeling. But I was very interested to see if 2.0 would be any quicker than the previous version, let alone a match for Lightroom
Overall, in my view 2.0's performance is definitely no worse than before, and Apple aren't strong-arming users into upgrading their hardware again (further evidence it's a 1.7?). And it is pretty clear that plenty of effort has indeed gone into making the program appear faster. So it quickly announces it has finished importing new pictures, even though to do anything useful with them you still have to wait while it quietly builds thumbnails and previews. Of course, speed that is apparent-only is no bad thing for the user, and helps the fanboys get away with blanket claims. But even when you define speed more a bit more tightly - as what really saves you time - I think one can point to Aperture 2.0 having taken some big steps forward.
One is Quick Preview mode (more here). You activate the mode by hitting the keyboard shortcut P (or via the button dumped down in the bottom right corner of the screen - yes, all those fiddly little buttons are still all over the place). Once in Preview mode, the program displays the JPEG preview that the camera added to the raw file, which means you can browse through pictures at lightning speed. You will not see any adjustments that you've made to the pictures, but that's irrelevant when you're under time pressure doing your initial review, working out what you've got and deciding on keepers and duds. I'd say Aperture 2.0's browsing speed is close to PhotoMechanic, the gold standard, and for some users that's going to be a big plus.
The other step forward is a bit of catch up with Lightroom. For this type of workflow application, the previous omission of background processing was little short of bizarre and meant you had to wait for big jobs to finish. Exports now happen in the background, so you can get on with other work while the program saves out TIFs or generates a web site. OK, things slow down a bit but you can't have it all - for some users, background processing of exports will greatly improve start to finish times.
So two days running, I say something nice about Aperture. Well, it is Valentine's Day.
PS For fair and balanced views of Aperture 2.0, see