While I never actually owned one, I built a lot of machines over the course of a year a while back with Shuttle's AV61.
As far a quality goes they were very well made, solid, and stable as hell in use... overall quality was excellent.
Overclocking apparently is not really a big concern at Shuttle (at least at the time) so don't expect to see a lot of speed tweaking options... they shoot more for reliability than speed it seems. And given that these were "business" machines I was constructing they certainly fit the bill perfectly. Never had a single RMA. And of all those machines only one problem in about a year and a half of operation. One board refused to soft-powerdown after being online for a little over a year. After going through the BIOS, Windows Settings, and swapping out the power supply just to be sure... I swapped the board and it cured the problem.
One failure out of about 50 in over a year I'd call a pretty good record.
If I had ONE complaint with Shuttle? it?s support? or more correctly? the lack of it. In a word? it?s pathetic.
Unless something?s changed over there, don?t think you?re going to get any quick answers out of Shuttle?s tech support staff. Initially, I had a problem with the first few I built. I ended up getting an answer off of their tech support board from another Shuttle user that a jumper setting in the manual was a misprint (if memory serves). Never heard from anyone at Shuttle at all? ever.
In fact, for about 2 or 3 months I gave the guy that was doing most of the actual ?support? on Shuttle?s support forum a hand in answering questions? and he wasn?t even an actual Shuttle rep, just a user. He told me that he?d never actually seen anyone from Shuttle post answers on their own board? that?s how bad it was.