I really like the GS tests TBR tests suck IMHO (PS decent, verbal rubbish and BS decent towards 6-7, did not like 1-4). GS I feel harks on the same few concepts and really gets them into you and I just feel overall is more high yield...i went into prep trusting TBR, but have drastically changed my mind. Oh and GS verbal isn't good either...I just skip the verbal.
And when you call them they're like: "oh our students here in california repeat EACH of the CBTS several (3-4) times..." yeah i'm sure they have the time to do that.
I've been scoring solid 11-12s on GS BS and PS and AAMC were around there as well +/-1. I think their revised scaling system is really accurate w/ respect to the AAMC CBTs (not sure how accurate with the real MCAT).