Sloppy work. I had a leak coming through my living room window after they installed it. Their own employee told me it was their fault for a gap in the caulking, but owner Steven Johnson says it's impossible to know for sure that it was their fault (even though his employee confirmed with a leak test, then repaired the problem by adding caulking).
Communication has been dreadful; they will go weeks to months without responding to me. I've been dealing with this issue now for 4 full months. If they'd just been straight with me from the beginning I probably wouldn't care as much, but I've just never seen such disorganized communication and blatant disregard for the customer. It's bad!