Not a bad game, but after all the rave and fascination people seem to have for the game (not to mention it's high status on the top paid/free games lists), I was underwhelmed when I finally played this the last time it went free. Guess I was thinking about the first time I played the "Death from Above" (think that was what it was called) mission in one of the Call of Duty games. To me that mission had a lot more tension and build up. Playing an app with that kind of gameplay but without that first adrenaline rush just got old pretty quickly.
Honestly, I thought it had gone completely freemium until I saw it on the paid lists again a few weeks ago at $.99.
Don't just rely on my opinion though. Obviously, there's plenty of people who love the game. Worth a free download to give it a shot at least.