Not buying Left for Dead

I think I'm passing on Left For Dead.  Considering it only has four scenarios and each scenario takes about 30 minutes to play that's 2 hours for 55 bucks.  Considering that downloadable scenarios for the 360 will probably be at the very least 400 points apiece, that could really add up.  I'll probably end up gameflying it or renting it at Blockbuster.   I'm glad IGN put that in their review. I just don't think the single player is worth going thru more than once cooperatively and the multiplayer just doesn't seem very good at all.  Shame on you Valve for charging 55 bucks for 2 hours of gameplay.  That's bad business in my book.