The AAF is aligning themselves up to be a developmental league more than any of the others. I've kept up with the league every week, it's decent football. Crowds are struggling in many of the markets including Arizona, Atlanta, and Salt Lake City. San Antonio has had the biggest crowds with 25k+ for both home games so far. For the most part, looks like the AAF is going to non-NFL markets (except Atlanta and Phoenix) like San Diego, San Antonio, Memphis, Salt Lake City, Orlando, and Birmingham where the XFL is going to the biggest TV markets (7 of 8 teams will share market with NFL team).
I think it's definitely a place where guys like Guyton can get some experience and try to move up to the NFL. Memphis is the worst team so far, and has already played three QBs. Manziel will be the biggest name in the league by far. Besides him, Garrett Gilbert (Orlando) is probably the biggest name behind center.