MKEAA, sorry this post is so late.
I learned some interesting things about Brazilian JJ recently.
In the case of the Gracies, if you spar with them, they will really restrict what moves you can make. Also, they like to start out with their hands and arms in a "high" position. When they do this, many will match this high stance, and when you do, they will dive low at you, and down you go.
They really like the arm bar, and I forget the proper name for the other technique they frequently use. The fact is, both of those moves can be easily(!) overcome, once you know how. This is not a slam on the Gracies, it's just that almost all martial arts have, IMHO, effective counter moves, and that makes them potentially less effective.