I upgraded to snow Leopard, and now my scanner no longer works. Apple TV was acting very flaky (no changes to the network) - turns out there was a problem with iTunes and Snow Leopard. My patience for Apple errors is pretty much at an end.
On the scanner, the software is now provided by Apple for many scanners and is accessed via the printer control panel or the application Image Capture. Works pretty well. But it takes some time to find it and get used to it.
Apple recently announced an upgrade for the Apple TV which I bet is to address this very situation.
Each time you upgrade an OS, you WILL have these issues. It is part of reality. Even updates need to be approached with some caution. I never update until I watch to see if some unintended problems have been caused. This occurs whether you are running OSX, Vista, XP or Linux.
I'm having the same problem with my Epson printer/copier/scanner. The scanner part works, the memory card reader works. Of course, the copier works. The printer is completely dead. I've tried everything I can find from Epson and Apple and still no dice. Everything worked fine with Tiger and Leopard.