We are still using Firefox 2.0 organizationally and it's very stable. We still have some sites that are not certified for 3.X, which I am monitoring closely. Like any forward thinking Admin, I have been running 3.0 and the 3.1 betas. I have found them to render faster, and they seem to scroll faster; however it seems to have come at great expense. CPU and memory usage is substantially higher. Can anyone else confirm this? I remember there was great debate concerning file handles and sqlite databases. Are these issues resolved? Right now, Firefox seems like it will be hard for me to scale to hundreds of people.
Here is a snapshot of my session on the server, with moderate usage for a few hours: