As promised, a little review of "Mugglenet.com's What Will Happen in Harry Potter 7".
In short, there is nothing in the book that hasn't been said somewhere on Mugglenet. Further, at points they base assumptions on assumptions--for example, in several places they assume that Harry is a Horcrux and base further analysis on that assumption.
But, despite that, I still liked the book. It hits all the real questions, and it discusses them in an organized fashion that isn't necessarily possible in a chat room or a single editorial. And realistically, at this point, it's impossible to even get to some of the big questions without doing a little bit of inference stacking so I think that's forgivable. In the main I think that even if the authors don't end up being right, they're thinking the right way.
So, if you want some good, well-organized, theorizing fun while your waiting for Book 7, I would recommend you go read.