Actually, the reason I use Ubuntu instead of Debian is that most language runtimes I use (python, for starters) were, for quite a few years, more up-to-date. Of course I could use unstable, but I'd much rather use Ubuntu's LTS and security updates.
Yes, Debian will pretty much just work, but back before 7.x it would also be a pain to support a number of applications (we mostly rolled our own builds of "modern" runtimes and libraries we had to use, with predictable lag times and dead ends). Ubuntu takes all of that pain away and has relatively new stuff, even on LTS (sometimes through backports, but hey... nobody's perfect).
I also left RedHat because of the way the distro evolved, but never jumped to CentOS because at that time yum was slower than molasses, and I'd much rather use a Debian derivative anyway.