Briefly, here's my 2 cents after 24 hours on Snow Leopard:

• New Exposé is teh suck. Windows no longer retain their relative sizes in Exposé, which means a full-screen window might appear the same size as your tiny chat window. This is pretty dumb. I don't know how it was decided to ruin the solid, usable Exposé of 10.4/10.5 with this lame replacement, but this change makes the usage of Exposé non-intuitive, and that's a very un-Apple thing to do. Also, what's with the tacky blue-border? Did the Apple UI designers quit and get replaced by a pack of squirrels?

• Another big ding on new Exposé: the way it uses available screen space to render your windows is really, really bad. Try using it with a small-ish number of windows, maybe 3 or 4. Notice all the wasted, unused space?

• 10.6 feels faster than 10.5, but can't give too much credit here because 10.5 felt much slower than 10.4. And this is significant because every other transition (10.1 to .2; 10.2 to .3; 10.3 to .4) all felt faster. So Apple is back to it's previous reputation of increasing speed with next 10.x release.

• 10.6 install did seem to free up several gigs of disk space, although I didn't measure how much. Their claim of "7 gb" seems reasonable.

• They finally made it possible to hide the Finder sidebar (where the little shortcuts hang out). I hate that thing, and I think it was 10.4 when they forced everyone to have the sidebar, like it or not. Enough griping, it took them a few years but reason finally prevailed, now you can hide the Finder sidebar with Command-Option-S (repeat to show again).