I guess no one wanted to answer your question.
Most reviews are nothing but thinly disguised pre-sell letter's.My feeling about most information products is that they are overpriced and outdated. By the time the "gurus" get around to hawking a "new" wonder system, the real innovators AKA SPAMMERS have already latched on to the next big thing
I know that opinion isn't popular but it is the truth.If you want to figure out how to market online then find a prolific spammer and reverse engineer where he is getting his backlinks from by using the yahoo site explorer or backlinkwatch.com.
as to your core question, I have found the reviews at imreportcard.com fairly helpful.