Just as much fun as 9.0 and 9.5 rated games in the genre.
Huge arsenal of awesome moves that you can master. Interesting diversity of missions - I would say although less crafted like GTA IV, I enjoyed each mission a helluva lot more than that clunky and slow experience.
All in all a nice jaunt of destruction which doesn't get as old as you'd think it would, even after hours and hours. The desire to get new powers is a major draw.
If you are waiting for some of the awesome games that are coming out soon, this will more than keep you occupied until then. That said it is worth noting that given the economic climate atm, you may want to make sure you are happy to invest the premium price to play it.
Hope this helps people hovering over the purchase button in steam ;)