Thank you very much for your post; I went out and bought this webcam after reading about your experience. I can confirm that the Logitech Quickcam 5000 Pro works with my G5 (2 x 2 GHz) and iBook G4 (1.2 GHz). I purchased it at Best Buy on sale for $60; every one they had came in the MS Vista & ©2006 packaging. I initially had problems with it working with my G5, but it had no problems working with my iBook. I eventually traced the problem on my G5 to a screwy Tiger installation (I had been having weird USB2 issues for quite a while in fact), and after I reinstalled Tiger, the Quickcam 5000 works just fine on my G5 too.
As for application compatibility... the camera is recognized without me needing to install a driver when using Skype, Yahoo Messenger, QuickTime Pro, and HackTV. However, when I try to use it with iChat, iChat always claims the webcam is busy - from all the other posts it seems iChatUSBCam should allow the camera to work with iChat. I personally haven't tried it because I use Skype to video chat with my GF (who uses a PC and the PC version of Skype). It's a little choppy, but I think it's because I'm on cable and she's on DSL. Also, I'm willing to live with some choppiness to use a $60 webcam instead of paying the ridiculous $300 it takes to buy an iSight on fleaBay nowadays.
Power Mac G5 (2 x 2GHz) NOT dual-core Mac OS X (10.4.8)