the only bugs i have really encountered in Jaguar have been brought over from 10.1. These have to do with waking from sleep and accessing the network. There have been quite a few times where the finder and all other programs hang trying to get access to a network. This happens even when it doesnt need network access. Sometimes I am able to fix it through the terminal, but most of the time things are so messed up that the shell wont even load.
What I DO like tho, is that even tho iChat is buggy, the instant messanging itself seems to be a service a la Proteus, and therefore when iChat crashes, I stay online. Then once I get iChat running again, I receive all messages sent during the time iChat was down. That is pretty damned good work.