Something to try in Virtualbox: http://plan9.bell-labs.com/plan9/download.html Personally I find the interface almost unusable, and the shell is weird and very lacking in features (e.g. no job control, ouch). Coming from Linux/UNIX it's pretty alien. One thing that does leap out at me though: unlike X11, Rio (the Plan9 display server) can do rubber band resizes properly, without needing to freeze the whole screen. Also the "rubber band" is bright red and several pixels wide (instead of the 1-2 pixels of inverted color common to X11 window managers). That, folks, is the sensible way to handle window movement and resize.
Monty Python's 'The Holy Grail' had a bunny, and I am pretty sure that must have been Glenda (the Plan9 mascot). I tried Plan9 years ago. And gave up almost instantly.