Been running Snow Leopard since yesterday. As Apple promised, on the surface, you can't really tell that anything is different. When you click on the dock, you notice the popup is different. You notice the stacks are different when you click on them. You notice the 20Gb (Yes, GB!) of space on the Harddrive that you get back. (20 on my machine at least.)
So far it's running like clockwork. If I run up against ill experience I'll make note and post it, but so far, it's running like a top.