Consider MacOS on a MacBook. I realize it's not Linux, but you avoid the trouble of installing and maintaining Linux.
Plus the Mac OS X desktop environment is nice. This is exactly what I need: native UNIX and a good desktop environment.
But yea, OS X does seem pretty nice, I'd probably give it a try if I didn't care about things like openness [1] and vendor lock-in [2].
[1] http://diveintomark.org/archives/2006/06/02/when-the-bough-breaks
[2] http://www.tbray.org/ongoing/When/200x/2005/09/18/Apple-XML
The only thing I can recall paying for is Parallels, a virtualizer similar to VMWare, to run MS Windows under MacOS. I hardly ever use it.