I've been using an unRAID setup (on an old workstation with plenty of bays) for a couple years now and I've been happy so far. No failures yet though so I haven't really put it to the test. The HP microserver definitely looks nice.

I just use it for storage though. No VMs etc. And I'm not overly concerned about access speeds so long as I can play HD video off it (which I can).

http://lime-technology.com/