I am finally going to try online tonight or tommorrow night, depending on work.
I just finished single player last night. I must say, not only is the normal FPS parts the best I've played, but the game has _way_ more variation of gameplay than any FPS I have played. Off the top of my head, I can think of 5 'mini-levels' where the game play is not type FPS.
I would say it took my 8~10 hours to complete. Though I can see if you are very good, and die rarely, 6 hours is possible. The game is good enough, that I just might play through the single player again (maybe Arcade mode), so I don't feel that $60 ws too much, especially when you factor in online play. BTW - I can't even remember the last time I played through a game twice. GOTY for me.
~S