I started with Red Hat, moved to Fedora Core (3,4,5,8); used CentOS, FreeBSD (both on my Mac and as a server install); Debian Feisty something, now have servers running Ubuntu Server 9.10 Karmic something. So far so good. I've installed both the 32-bit and 64-bit version and it's working pretty well.
-Getting started. Had some funky issues with the full install iso. Worked great with the minimal install CD/disk image.
-Have to get used to the Debian way of doing things. But once you figure out the weirdness (and when you bump up against problems that just don't exist in RedHat/Fedora/CentOS), you learn to look for the Debian exception et voila, you find there's a reason and a method to overcome the problem.
-Apt-get: The binary package installer. Almost as good as yum, but the packages it installs, plus how it resolves dependencies, seems to be more robust. The current version handles all the PHP5 issues pretty well, (unlike CentOS, RedHat, Fedora). If you like PECL, it installs it. You like apt-get, you can use that too.
-Directory structure: I always thought that the RedHat directory structure was kind of random. I pictured a mushroom chewing, chronic-affected North Carolina hippie coming up with their directory structure. Debian's approach to organization is a nice balance between ideosynchratic artistry and Prussian organization. I can usually intuit where things are with Debian. A big plus.
-Ubuntu desktop. Basic. Nowhere near OS X, but pretty good. If I could just figure out how to tunnel x11 and run the interface remotely on my Mac, I'd probably dump vim forever.
-apt-get. I really like this application. It does all the OCD cleanup stuff I believe in, without the pain.
So, for the forseeable future, my preferences lie with Ubuntu Server. Don't know much about the company, but the community looks pretty good. And I'm just happy to have a good, stable version of PHP5.2 with pecl working without any hassle.