Criticism
Pros:
Spaces is really really nice. I'm already using 3, so I'm glad it scales up to 16. That's 28,224,000 pixels of joy!
I like some of the new iChat stuff.
Things seem a bit snappier overall.
Safari seems more compliant with web standards than before.
Cons (sadly the longer list):
Translucent menu bar is utter crap. Until there is some solution to this, I will not be installing on any more of my computers.
Dock is worse.
This is better, but the new dock takes up more space for the same size icons, so in order to reclaim your precious screen space, you need to have a dock with smaller icons. Still, with a light desktop image, it looks like a dark pit of doom. I look forward to hacks to make the dock lighter.
The new folder icons are atrocious. I thought we had moved past flat folder icons with OS 8. They look bland and ugly.
Window shadows are considerably darker and longer than in 10.4. This, along with translucent menu bar, darker dock, darker windows, and overall lack of color make this the most depressing OS X ever. Macs are supposed to be cheerful and bright. Leopard is just dull and dark.
Mini-windows, or whatever you'd call them, that only appear when the app they belong to is at the front, now have their close buttons red even when you are not mousing over them.
I'm sure I'll get used to some of these things, but currently I will not be switching over completely until there's a fix for the menu bar and the window shadows.