so far I'm experiencing.. -> XL-1000 (having 4 units)
no problem at all, if you have stock cpu( fanless), you just do nothing, just add Harddrive or utilize the DOC.
if you upgrades the cpu to 350 -up (mine: 450Mhz), need to add (fan-heatsink), low profile, around $10, I bought a bunch of that, for make my life a little bit easy:).
The VGA display, is kind of weak though.. if you want to use as a graphical terminal(it's ok, for generic usage)
I installed Linux and don't know about the windows. actually serve me as a headless units. planning to use "openmosix" - distributed parallel machine (similar as "beowulf" but different concept). could be my small and thiniest linux machine, which I have.
so far that I experiencing, hope this info would help U.