I use CentOS 6.x almost exclusively, since I work with several different low-end VPS for my businesses. I found it's much, much easier to have adopted a sort of "let it fail" philosophy and replicate across many (then worry about the failure when I have time) instead of paying dearly for a single high-end VPS that does occasionally have downtime. I'm also "sort of" in the business of CDN-type services, so geographical/latency distance is important to me, which is another reason this "let it fail" across many replicated servers around the world works best for my situation.

For hardware firewall/security appliance, I use pfSense (a FreeBSD "distro").

That was the case when I ran Linux on my server. I used Debian and so my (non-Windows)desktop was also Debian. I followed the trend to Ubuntu, but now I'm on OpenBSD for the server and kept Ubuntu for the desktop.

I used to do the same kind of thing, but now I just run OSX full-time because I like the user experience, and Vagrant virtual dev environments let me run whatever distro I want.

Actually, for me it was the other way around. It was only natural to use Debian for my servers when I used it already at home :)

Not really. I'm running Ubuntu on my server, but vastly prefer Arch.

This is exactly why I use fedora too, however I'm increasingly pulled towards Ubuntu again....

Is there any reason you'd use Ubuntu over an Ubuntu-like distro such as Linux Mint? I'm just curious, because I feel like not many people know about Mint here, and the general feeling is that people don't want to use Ubuntu, but like apt and the Ubuntu repos (which Mint uses, without so much of the bloat of Ubuntu, and with a different UI like Cinnamon, which is fantastic).

Not quite servers, but I used to work in a lab where we used mostly RHEL/CentOS for our scientific computing work.

I found myself gravitating towards RPM-based distros during that time.

Yes. CentOS minimal for servers, Fedora for desktop

Not for me. It actually keeps me on my toes a bit regarding differences in distros, especially since I have done well taking on project where server (mis)configuration was an issue as well other devs were struggling with.