I've been getting into Plan 9 this year; I love the simplicity of the design, such as the fact that nearly all system services are accessible through the file system. I'm running 9legacy on a spare Intel Core i3 mini-PC; my ThinkPad USB keyboard works very well with the rio and acme interfaces, which need a three-button mouse.

Admittedly I'm also using Plan 9 as a platform for my own OS project; I feel I can express my ideas easier using Plan 9's infrastructure compared to using Linux or one of the BSDs as a foundation, though this comes at the cost of extensive driver and software support (for example, there are no Common Lisp implementations for Plan 9 that I'm aware of, and porting an existing implementation such as SBCL will be a lot of work).