I am currently using Ubuntu 12.10 on 2 servers, which seems to be stable. I had a few little problems with bind stopping for no reason on one server, and a couple of other little weird problems, but cant remember exactly what they were. Reinstalled and it seemed to have fixed them.
I also have servers running RHEL/Centos 6.3 and i prefer this to ubuntu. Plus the added benefit of being able to do an install via VNC..