We have CentOS / RHEL foisted upon us at work. I run Ubuntu at home, but honestly, it's 6 of one, half-dozen of the other as far as I'm concerned, at least for the server side of things. I run Mint for desktop use. Basically Ubuntu with Cinnamon on it.
SmartOS is my current experimentation for server OS. It's a fork of Illumos which was Sun Open Solaris which Oracle took back causing the name change. Any way I think it's an amazing server platform as they perfected the Solaris zone container technology which was the pre cursor to Docker and I think it's way better than Docker.
Isn't it better just to do a local (limited) repo at that point and block its access to teh internets? I mean, you still want to have the ability to do a corporate network wide update in case of another huge issue like Heartbleed.
I am looking to upgrade my front end desktop: I would like to upgrade my monitors to 4k with an AMD gfx card to drive them over DP using OSS drivers and Mesa stack.
I still use an old Fedora 19 with Compiz and Mate and a newer kernel with BFQ and BFS for my workstation but it is starting to creak around the edges as it is hand managed .
Problem of forced upgrade: I need a newer distro with new X, kernel and gfx card mesa stack that works with Compiz + mate or desktop that provides SIMILAR functionality. It has to drive 3 4k monitors over DP.
When I upgrade I would like to keep the same functionality I have now so as not to have to screw around with my workflow any if at all.
 3 displays (4k over DP)
 and a 3x8 virtual desktop grid, sometimes bigger depending on what Im working on.
 I use 3 important Compiz plugins for navigation of desktop grid, and window selection and movement between desktops
a) * Expo plugin: shows 24 desktops accross 3 monitors, use for switching/moving/drag/dropping stuff between desktops
b) * Scale: window picker for current desktop and ALL 24 desktops
can quickly scan all windows, click to zoom in/out, browse, then select to go to right desktop
c) * plugins to slide between desktops and shortcuts to send windows directly to 1 of 24 desktops
I mostly use Arch for personal / regular computer stuff and Kali for work. I do like Ubuntu quite a bit but have moved over to Arch full time unless something at work requires a user friendly Linux OS. My co-worker swears by Mint but I don't see the big difference and with their lackluster security errors I tend to just stick with Ubuntu when needed.
Fedora, Ubuntu, Pentoo, Kali (of course), and raspian. I tried Puppy for an ancient laptop I had, worked ok but I forgot what I was even doing with that project. Strong preference for Fedora. My server is getting delivered on Monday and then I will be at one with the universe. Right now I just run a couple of VMs off my laptop.
I guess a lot of pentesters are using Ubuntu/PTF but I'm not really on that level where I need some specialized rig.
I plan on hitting up a wireless CTF in April and failing terribly at it, so boning up on Pentoo.