Here are my observations after using Snow Leopard for a while:
Better: It does seem faster in areas such as networking. But that may be because I was having so much trouble with Leopard networking, that anything is better.
Bug: There’s a bug in Mail where Smart Mailboxes always sort by Subject. I can change it, but the next time I relaunch Mail, it’s back sorting by Subject again. Extremely annoying. [Update: With some judicious editing of a .plist file, I managed to make it so that it always sorts by date. Better, but needs to be fixed.]
Feature: I do like the new white text on black background menus in the dock. I shouldn’t though, because they’re different than the menu bar. I prefer consistency to cuteness, so maybe Apple should try this look in other menus.

I’m cursing all you guys at Apple who came out with a new Shuffle before I could complete my voluminous postings on the old Shuffle. “He who hesitates is lost.”