I have had the FrankenTurbo F4 (Mk1 original model) in my car since February of 2010.
I have about 35,000 miles on it and no issues. I had the turbo off a months ago when I was changing out my cv joints. (SO much easier to get the turbo out with the CV's out of the way). There was no play in the shaft at all, the compressor still looked brand new with no noticeable wear, and the turbine looked as you would expect from all the exhaust.
I have it tuned with Motoza tuning and it easily holds 20psi to redline. I was one of the originals to get an EGT probe as well and the temps were well within safe range from what I remember (Its been removed for sometime now)
The only thing negative I could mention, there is a lot more oil in my intercooler system then there ever was with my K03s, but it does not seem to be an issue at all.
Customer service is great. I could never say enough about Doug. To this day, I will email him with a concern and he will respond quicker then any other company I have ordered from.
Just as a story of how great my experience was with Doug, when I was installing the turbo, I snapped a bolt for the exhaust manifold to turbo and could not back it out of the turbine side. Doug overnighted me a new turbine housing to get my car back on the road ASAP.
If you have any specific questions, ask.