I have 2 Micro-ATX machines that I used to run them on, I went back to a more traditional fanless PSU solution when I started getting strange problems with the system halting all the time.

I think it was a heat problem of some kind, I also found they really stressed the external 12v PSU bricks I was using at the time. I wouldn't use them again myself, but the machines I am using are pretty much sealed 1U rackmount servers and I think that type of PSU needs a little more venting than I had available.

Cheers

Cris.