I've been running Bon Echo (Firefox 2.0) for months now. I've been really happy with it. One of my favorite features is "Session Restore." (After spell-check in text boxes, something I'm using as we speak)
A while back I had the epiphany that if I force quit when upgrading, after the update, it'll ask me if I want to restore my session, and I just got a seamless upgrade! [*]
I haven't started a new session in months. I have boatloads of tabs that hold items I want to act on but haven't yet.
I guess they changed the session restore functionality between RC2 & RC3, and didn't bother to DtRT. I just started RC3, and was staring at a blank page. I just opened a bunch of my standard tabs, and tested session restore and it worked.
I'm not even sure I can guess at half of what I lost. Serves me right, I know, but still.
I thought I should warn anyone else who was similarly clever.
[*] This is also handy because having FF running for months on end seems to make the system (not FF) CPU utilization max out. It happens faster if I sleep the machine. Given this is a laptop that I take on the train, that's a bad thing.