Matt Fraction wrote a very good review of 52 at his website. Check it out here. I think his biggest point is a strong one - 52 definitely built upon itself, making the end bits feel tremendously dynamic (it doesn't make the earlier issues better, though) - as though the early issues were the rollercoaster going up the hill and the later ones were coming down. A good deal of fun.
Marvel 'Leaks' Weapon Plus Paperwork for Wolverine, Captain America