- Installation works fine (but, as always, takes ages to complete)
- Updating works except for Illustrator, since someone at Adobe thought it would be a great idea to use a PowerPC-only patching application
- The license agreement screen looks funny and you can't see the buttons until you scroll the window contents
I haven't really used it yet, so I assume there are more problems waiting. If you rely on CS3 for daily work, I would definitely wait before upgrading.
Also, I wouldn't count on Adobe releasing an update, or at least fixing the broken Illustrator update. Back when Snow Leopard was released (less than a year after I bought CS3, which is still the single most expensive piece of software I own) and a few problems showed up, Adobe didn't care either.