No problems with iChat here. Been running beta since it became available. Very few issues, so far. Most noticeable issue was with a couple of 3rd party widgets. One's been fixed by the developer, the other two I fixed myself.
Had one hang while playing Pogo game a few minutes ago, but very hard to say it was specifically related to 3.0. Once in a while, these cropped up in 2.x.
Overall, I haven't had anything happen bad enough to remove the beta. I'm enjoying the speed - it's significantly faster overall than 2.x.
edit: The uninstaller seemed to work fine for me also. I reverted back to 2.x shortly after installing the beta, to check something out. Then, reinstalled the beta.