I believe several people have answered this question already. I personally am using Chad's videos as my primary review for everything and EK lecture as secondary for sections I know pretty well and BR for secondary for sections I don't know as well (bio).. I've seen tremendous improvement, at least in my general chem review, which is all I have fully studied thus far. I'm writing on 8/16 so I will be of more help after I finish reviewing for everything (hopefully 7/15).