I just installed 10.04 on an HP mini (using it now). Is the server edition that far behind the curve or are you just being conservative?
BTW, I frikkin love Ubuntu. It's going to seep into the market quietly over the next couple/few years. I'm so glad to see Gates and Jobs having some of their market taken away, even if it's only a couple of percentage points.
If you use Ubuntu as a notebook/desktop, check out Guake if you're unfamiliar with it:
Initially, when I set this server up, I wanted to just leave it as 8.04 since that's a long term support versions (LTS). My theory then was upgrades were generally bad news, and so doing fewer of them is best.
However, I upgraded a laptop to 10.04 (the new LTS version) and was not pleased with the results. The initial install went fine but then on boot up the screen would go blank. The problem was 10.04 didn't recognize the limits of my laptop's screen (its about 6 years old). I fixed that manually, but now it has some sort of hang problem, perhaps related to the screen saver.
So... my confidence in 10.04 is a bit shaken, and I'm not upgrading my home server to it until I get more confidence in it. That'll probably not be before the next version (10.10?) comes out.
For the server, I don't need the latest and greatest. What I need is stability, and older versions with all the patches in place give me that. And that means upgrading more conservatively. I'll upgrade it to 9.10 and stop there for now.