I also discovered the not-so-smooth animation problem when opening and closing new program windows. On every computer I could check I verified this nuisance. But I don't think, that the drivers are to blame here...
Win7 is said to rely on hardware 2d-funcitons for zooming and displaying its windows. If this wouldn't work properly, the whole desktop should be a mess... I rather seems to me, that since the animations are calculated in realtime (think about all the possible
windowsizes!), this calculation isn't right.
Namely, the zooming decelerates too quickly for the amount of time the animation is supposed to take, resulting in never reaching the final size its supposed to. And since after the animation finished, the program window is redrawn in its original size, the
gap between these two size looks like the window is finally "popping up". The magnifying tool strangely seems to reset parameters used for these calculations... I don't know - it's a mistery! :)
You could actually test the slowlyness of Aero by opening the task manager, maximizing its windows, switch to services and playing around with the columnsizes. At leat on all of the computers I checked, well, that was slow!
Maybe the rumors are right, and ATI as well as Nvidea has stripped their chips from all 2d-hardware-acceleration. Then Direct2D wouldn't be of any help here and rather slows everything down! I guess someone with an old vga-card (>3-4 years) should check there,
but then Aero wouldn't work anyway, right?