I've been a staunch Ubuntu guy (more recently Debian) for years, I provide free hosting from a Debian based server and produced my Linux Integration Workshop based on the Ubuntu Desktop release, however client needs have recently pushed me to look elsewhere for my server platform.
It's basically down to online merchant security. I have a client running Ubuntu 10.04LTS in a Linode, who needs installed packages (i.e Apache, PHP etc) to be the most recent version releases in order to comply with the latest PCI-DSS scan requirements. Ubuntu 10.04, although an LTS (5 year long term service release) doesn't deliver up to date package versions from its repos, which is somewhat annoying and requires back porting from the more recent distro repos to patch (I'm not a fan of manual installs in this instance), a workaround yes but not the cleanest, and, still a 'workaround'. What I needed was a rolling distro offering the most up to date versions of all packages at every upgrade, a bit like the Mint LMDE, but server based, i.e a distribution you only ever have to install once, and once only.