When Ubuntu came out with Warty Warthog i was hooked.
For me Ubuntu made the first usable Desktop-Debian , and used it happily, until Debian Etch came out, a (for me) usable Debian based distro which was actually Debian!!
I am pretty sure many Ubuntu users of the first hour tried Debian (Sarge), wanting to use Debian, but somehow did not find the needed usability.
If you are a Ubuntu user with a fair amount of experience and would like to return in Debian’ s lap, in my opinion now is the time. And remember, Ubuntu needs Debian!
Etch is already becoming stale for the desktop, but Lenny is very much a usable (if not better) Ubuntu replacement.
Servers should of course stick to Debian-Etch for the obvious security reasons.