I also know of several colleagues that use and enjoy Ubuntu (because Unity notwithstanding, the distribution is pretty solid) with an alternative environment like xmonad.
My experience with Debian is limited to servers, but I'd imagine a lot of the creature comforts of Ubuntu are missing on Debian when used as a personal OS.
I think ubuntu LTS gets packages from wheezy and normal ubuntu from sid.
I like Debian for servers but I'd probably go with Ubuntu or Mint for desktops if I ran a linux desktop.
It's supported by a company called Canonical, but I'm not sure it adds value.
The community is larger and you may find online resources more easily.
I wouldn't be the slightest bit surprised if Shuttleworth sees himself as the "Steve Jobs" of Linux and with the direction they're taking, I think Ubuntu will be like Android/Linux (ie still "Linux", but largely incompatible with the traditional desktop Linux ecosystem).
Hopefully I'm wrong. But Shuttleworth has done little to give me confidence.