The bad far outweighs the good when it comes to posts on the forums. that being said if your truck is stock then you should be OK, with the ATS stage 2.
The shops that I've heard of people having great success with and are pleased with are
Brians Truck Shop
Suncoast Converters (Ft. Walton Beach Fl)
Monster box from factory tech transmissions
Racer X
John Woods
The oldest and most well known is BTS, at least among the ford followers. the others are newer to the game but have been around for a few years, long enough to determine their reliability and many if not all of these shops will ship you the transmission and all you'll need to do is swap it out and send the core back.