My original plan was to build a little air-cooled Linux box in the small, clear-plexi "Bob Slay" case from Mountain Mods. However, although well designed, the case is so small that a big (or even a medium sized) CPU cooler did not fit -- at least for most LGA 775 Mobo's with the CPU socket close to the edge of the board. Given that I had a Pentium-D CPU that runs pretty hot, I knew I would need substantial cooling, and was frustrated that I couldn't get a decent air cooling solution in place. I even tried mounting the intake fan outside the box, to allow more room for the CPU cooler, but that didn't look too good. The solution, of course, was to go with liquid cooling.
The case has the Mobo on top -- which looks fantastic, but also means there is not enough clearance above the video card to install a VGA Waterblock. Another factor to consider is that a full-length video card blocks the airflow in the top portion of the case. However, as the box will be used as a Linux Server, the demands on the video card are slight, and a short, air-cooled VGA card works fine for my needs and allows for good airflow.
The lower section of the stock case is cooled only by the exhaust fan in the PSU, but has no air intake. Also, the tolerance in the case is so close that SATA drives (with slightly longer power connectors than PATA drives) did not fit as intended. I considered drilling a hole and installing an intake fan for the hard drives, but having already decided to go with liquid cooling, decided to liquid cool the hard drives as well. I drilled a 120mm hole in the lower section of the case to vent the radiator, and fitted the unused drive bay with a venting panel salvaged from an old server case to allow for some air intake.
Overall, the box runs great, and is quiet, with substantial cooling headroom. Despite some struggles with the case -- and there are always tradeoffs when using a small case -- I am very happy with the Mountain Mods case, and would (and may) use it again on future projects.