Sheesh, gone are the days when you would buy a game, know exactly what you're getting, and be done with it. These days, people are screaming for DLC, and some complain about paying for it. This is silly to me, most DLC is post-production, and costs money (albeit low amounts of money compared to during actual production of the game). Not to mention updates to fix bugs, exploits, etc. Who cares if you're paying $7 or $10 for some good extra content? Isn't it worth it?
MS is one of the 'best' businesses out there, of course they're going to charge for something they can make good money off of, any large/good company should. I would be disappointed in them if they didn't. That being said, L4D2 is more of a PC game to me. I play MW1+2 and Halo 3 and whatever else on the Xbox, but there's something about L4D that feels wrong on a console.
L4D2 is one of my 'happiest' game purchases this year. L4D2, NSMBW (that I'm getting soon), and MW2 will keep my busy even during the craziness that is 2010.