I'm upgrading my main machine right now to 12.04 beta. I'm a little worried about stability but 11.10's kernel causes GPU lockups (relatively new computer) and the mainline kernel with 11.10 causes the Network Manager to go haywire and disconnect every few minutes which is very annoying in any interactive ssh app. Ubuntu came a long way but there are always those little things with Linux (at which point I'm reminded by HN that at least no one will be remotely disabling my software).
EDIT: Is HUD enabled/installed by default?
EDIT2: Yes, it is (tap alt and then your query).
From my experience 12.04 is quite stable, you are going to see a few app crashed reports but apart from that everything should work.
And I agree, Ubuntu (as well as other Linux distros) has come a long way. 4 years ago there was no way I could get my graphics card to work, today it works both on open source and propriety drivers. Amazing!
EDIT: Is HUD enabled/installed by default? EDIT2: Yes, it is (tap alt and then your query).