I took my AFAA course in 2003 and found it to be pretty basic. The reason I took it at the time was scheduling. I needed the cert. and it just happened to be offered that same weekend. Another reason I took it was I teach group classes (Spinning/Cycling) and AFAA is pretty much the standard for group teaching.
I do think certs from the American College of Sports Medicine, NASM, and NSCA carry more weight and they are more difficult. These work well if you are planning to go into coaching as well as training.
AFAA is not the toughest cert to obtain but overall, it's not a bad way to go, especially if you're planning to do any group classes.
Hope this helps!