Honestly, for what they cost I was never impressed. I used to work for a company that sold them for a while and they had all sorts of problems, including the finish flaking off. And honestly there are a lot of sharp corners on them.
Their warranty wasn't all that great (they really liked to blame problems on anything else) and the way they attached their handguards is quite old and antiquated.
The quality of the materials and the machining was quite nice in most cases, but honestly there are a ton of better manufacturers. ATRS by leaps and bounds; as well as Daniel Defense or you could go with stuff like MEGA Arms (CTCSupplies has them) for a really nice billet receiver set.