Snow Leopard was released on Friday, and I decided to dedicate my weekend to trying it out. All-in-all, it's much snappier than Leopard, especially regarding boot times and disk mounting/unmounting, but it does have a few minor annoyances.
⌘-tab and Mouse Wheel
If you hit ⌘-tab and then let go of tab while holding down ⌘, you can scroll through the list of open applications with your mouse wheel. In Tiger, scrolling down would select the application to the right and scrolling up would select the application to the left. This was reversed in Leopard, and I remember taking a few days to acclimatize. And now, Snow Leopard has changed it back to the way it was in Tiger. A minor annoyance, but something to get used to again.
I haven't decided whether I like the new style of Exposé yet. In Leopard, the windows were arranged with their relative sizes easily discernible and in a manner that mirrored their spatial positions.
Snow Leopard, on on the other hand, displays them in a grid structure. If that weren't enough, if you use Exposé on just the windows for a specific application, the windows in the background disappear and a dimmed version of the desktop is displayed in the background.
But the worst change, is the highlight method. In Leopard, when you mouseover a window in Exposé, you would get a transparent color overlay. In Snow Leopard, you get a color outline with blurred edges and a width of about 10 pixels. Subtle? No.
The other annoyance is the following: When you select one of the windows in an open application and then trigger Exposé for that application, all the application windows would come to the foreground. In Snow Leopard, this is no longer the case, although I'm holding out for this to be changed in an update.