EDIT: This question was expanded to include other Unix-like distros such as Hurd and BSD.
Before anyone wonders, I did read related questions and answers; I think I have a sufficiently unique question to give it its own page. I'm considering using my next computer in a multi-OS way, with a very thin host operating system and multiple virtual machines (typically not running simultaneously).
Why? I'd like more flexibility for experimenting with unfamiliar distros than dual-booting offers. I heard that Windows 8 refuses to share a hard drive with anything else, and as I'm a developer I expect to be using it but don't want to give it its own machine. And sometimes I do want to have two operating systems running side-by-side.
I understand this can be a highly subjective question, but maybe I can narrow it down enough. Requirements:
- uber-thin, in both RAM and HDD. I don't need applications other than maybe a package-manager and/or curses browser (to go grab VirtualBox and anything else I suddenly want). Depending on how much I use the host, I might install a graphical browser.
- a graphical desktop, although booting to a CLI with commands for the virtual machines would be fine. I'm comfortable using a CLI when I know the command, but can't live in it constantly.
- stable. I want to install it and forget it; I should barely know there's an operating system under the operating system, but it should be ready for me to use it if the guest OS breaks or I need to do something too heavy for a VM (such as use a remote desktop client).
- healthy community. I'll have questions; I need a community to answer them. A lot of projects would be a plus, but mostly I'll be installing to the guest operating systems anyway.
- decent usability. I like having nitty-gritty details hidden from me. deb is nice and apt-get is nicer, but I can compile from source. If it's a common task, it should be straightforward to accomplish - preferably one click or simple command. I can read manpages and build complex commands, but it's not a hobby.
I do prefer the GNOME desktop as it was circa 2009. I can use KDE or get used to any other desktop if I need to.