I installed Snow Leopard on Tuesday with little hassle. Almost annoying little hassle. Nothing went wrong. Nothing broke. It was almost disappointing there was nothing to fix or change. So far the most detrimental thing that happened was that Snow Leopard made a few screen savers obsolete, but my favourite one (Pong Saver) has been updated for Snow Leopard already anyway.
My impressions: favourable. The only large tweaks I've noticed are Expose and stacks (and faster startup and shutdown). The new iTunes (and iPod Touch) software that also came out a few days ago have been a welcome addition. As well as the nicely redesigned app store.
I still have a few projects hanging around to which I need to get, and hopefully will have something interesting to post soon.