I think Ubuntu 12.04 LTS is one of the most stable operating systems I’ve ever used, deserving of the “Long Term Support” label.
I haven’t been as happy with later releases. I still run 12.04 on two machines, but my work machine is running Raunchy Ramjet. It tends to die in a spectacular way a couple of times a week (always Compiz) but now I’m getting some weirdness in the unread count for Thunderbird.
I am very e-mail driven, so I always find myself looking up to the left hand corner of the screen to see if I have any new mail. While it works some of the time, quite frequently the unread counter is missing when I have a number of unread messages. But what I thought was even weirder was that once the indicator actually looked crooked:
Odd huh. Haven’t seen it since, however.
Still wish I could get .WAV files to play properly on 13.04.