I've been a member of OBC for about two years. Sometimes I'm not very active, and sometimes I am, just depending on my free time. I've been an avid reader for as long as I can remember, so I was ecstatic when I stumbled across this site that would actually pay me to read and review books. I've only reviewed about ten books in all, but I enjoy occasionally having a "job" that is totally book related.
Most of the time that I'm on the site has nothing to do with the book I'm reviewing. I'm looking up discussions for other books I've read in the past and reading other reviews for books that I may be interested in. Yes, while I do get paid a small amount for writing reviews (which honestly is nothing to write home about), I've also spent a fair share of money on buying the books that others have reviewed on this site. These are books that I never would have heard of outside of OBC.
I agree that sometimes editing scores on reviews are a little inconsistent. But the hoops that the reviewers must go through are all to ensure that the author is getting the best quality review available. My overall experience with the site has been overwhelmingly positive.