Every year or so, I get the urge to replace Xubuntu with Debian on my desktop and development systems. Sadly, it just doesn't make sense to do so. Ubuntu still has a few huge advantages over Debian. In particular:
Ubuntu's bug tracking system is far more convenient than Debian's, provides richer categorization and relation tools, and integrates with upstream trackers. I waste less time when I have to report problems, and since more people are sharing knowledge in launchpad, I also waste less time on diagnostics and fixes. Average users find it more approachable, too, and can often use it to find a workarounds for problems that they need solved before the next Debian release cycle crawls around.
Ubuntu's personal package archive system is both a public build farm and an open software repository. This means I can share custom software packages with others, with no bureaucratic overhead, on any release schedule I choose, through a channel that's extraordinarily easy for users to install, with integration into the standard system update process. Oh, and I don't have to set up build environments for multiple architectures (or in some cases, any build environment at all). Of course, all of this also benefits non-developers, by giving them access to a lot of software that isn't part of the Debian archive.
Last time I checked, Ubuntu still had far better support for certain important hardware components, like my graphics card. I'm an advanced user, so I could probably jump through the hoops to get proprietary drivers working in Debian, but most people don't have that kind of knowledge or the time/inclination to develop it. I wish there was a way around this by simply choosing different hardware, but there simply is no good substitute for certain proprietary devices. (Linux gamers can either use nVidia hardware with the closed driver, or be stuck with inferior performance.)
Despite Ubuntu making some dumb decisions and pissing me off at times, it honestly has done a lot to advance linux. I'd like to switch to Debian, but honestly, it would just make my life harder. I hope it catches up soon.