We were using Lenny. ( Well Sid, really ). Had to do that for development. I upgraded my server with ubuntu 10.04, for a different project. Noticed the packages. Wearing my developer hat, it's a no brainer. Everything we need is there.
I'm the admin as well. We might need more than one "box" (running on VPS for now). I do not want to build things that apt would put on for me. It's not hard, but I'm going to need that time.
The debian "box" has a bunch of stuff on it, that'll have to be integrated properly, but I think we are going live in a distressingly short time. (Just found out.)
I am aware of the reflexive answers to this question. What I would like to ask is are there critical bugs or critical instabilities that would make one shy away from the ubuntu/server path? I could not find any bugs that would stop me, but perhaps there is something?