with bug fixes by Ubuntu devs (which get backported to Debian), some cooler packaging, and a better driver selection. I thought everyone in the Linux scene who's been around for any significant length of time knew this.. For more details, read Ubuntu is based on Debian unstable
I would say that Debian has a certain importance to the Ubuntu community, given that if Debian disappeared, the Ubuntu community would have to whip up all these cool new packages from scratch rather than fixing what's broken from unstable and adding non-free drivers and cool packaging. If Debian disappeared from the face of the earth today, Natty might come out on time... but with luck, its successor might come out in 2 or 3 years. Or maybe Canonical goes bankrupt and it never comes out at all.
I switched from Debian Lenny because of the better driver (as in non-free) selection in Ubuntu, I had to get my new motherboard running immediately
I think Ubuntu (I use Kubuntu Meerkat) is a better desktop distro, it was intended for ease of use, which is important for most people who make a living with computers in an office environment and pretty much succeeds. If I were going to run a server, I'd put Debian Stable or Testing on it.