I've just finished 3 Kaplan topicals for G. Chem. And, while I didn't do so hot (65% on the first, 73% on the next two) I think they're absolutely golden material. When I get an answer wrong I ALWAYS learn something awesome. I'm not feeling too bad about the scores b/c I think that they're just hard, and I usually get tricked with funky calculations rather than not knowing how to approach the problem.
With only 3 weeks to go, I'm very sad to say I've done far less practice problems than I would have liked and, in all honesty, if I could redo everything I would probably have signed up for the Kaplan online course b/c the materials I've seen from them are great! They REALLY make you think. The only thing that I've used that may make you think more (although the questions are less "tricky") are the questions from the TPR In Class Compendium.
Like I said, if I could do it again I would have made my content review short and sweet, and then just pounded the hell out of practice problems b/c that's where the real payoff is. Live and learn, and hopefully I've learned in time to get a competitive score on the MCAT for a CA resident.
I'd highly recommend people use these topicals if they can get their hands on them.