Linux Users / Ununtu, Mint, etc...
Yes, but the BSD based derivatives are favored here. Slackware is the main-stay, but I've written one or two also that are used in-house, as well as a SLAX derivative for an Open Source project well known in some circles, and a current project to re-write an OS specifically for that same project.
Tom'sRTBT is still in the toolbox.
Also SuSE and one or two other SystemV derivatives, and some "real" unix, such as QNX.
I did multi-boots for a while, using the NT loader as I found it quite versatile at the time.
( Win9x can dual-boot too, but it's not nearly as versatile )
Next, multi-boot using LILO as it's even more versatile.
These days, almost any OS I care to investigate, but generally within a virtual machine.
The main-stays on the most used machines are all Linux derivatives, Linux itself derived from what used to be unix, primarily because of the versatilities. There is a Win2003Server machine, and a few others for specific purposes though. As a part time IT guy, it helps to know what one is talking about, so it pays ( literally ) to have the means to investigate whatever may come up.
Mixed environments are rare, but they are out there, so interactivity is also important. ( to me )
That's also why my main stays are not Ubunto, or any of the "Windows-like" M$ imitations. Those are fine for what they are, but like Micro$oft, hide too much from the administrator to be of any real educational value "under the hood" so to speak.
So far, the only OS I've been unable to look into, is Vista, because it's far too deliberately incompatible with almost everything, and has too stringent hardware requirements.
Just got the Win7 CD, a Vista derivative, but the reports are excellent, so we'll see....
The original thread intent, yes. In this little corner, primarily Slackware 10.x with the FVWM window manager, and TKDesk as the primary "desktop" when using a GUI. Some KDE apps, but KDE itself is as buggy as M$ Windows, just as bloated, but doesn't *need* the KDE desktop or window manager for the apps to work. Some of the K-apps are truly great, but all have "features" one will love, and "features" one will hate, much like M$ Windows.
Those that seek to be all things to all people typically fall short of that mark, but by mix-n-match one can come up with a perfectly acceptable combination.