Took my boat motor in to have it rebuilt after the top cylinder blew. They rebuilt the motor, replaced the black box, rebuilt the carb, etc. I got it back and it seemed to run rough. The explanation was that it was probably the 25:1 fuel mixture being used during the break-in period.
Pros: I'm trying... nope - can't think of anything.
Cons: Slow, Can't diagnose, won't stand behind work, poor wiring quality.