The only real reason this is an issue anyway is because L4D is an online, multiplayer game. If this was your run-of-the-mill, story driven, single player FPS the fans would be PRAISING Valve for releasing 2 so quickly since 90% of them would have beaten the game inside of a month and would be drooling for a follow up.

These boycotters are just cheapskates that are worried that everyone will move on to L4D2 and leave them behind, too cheap to buy the new one, stuck playing the old one with the other cheapskates like themself. At least that's how I see it. I don't really think they have much to worry about though, the two games have a vastly different style and I'm sure I'll switch back and forth between the darker, more gritty original and the lighter, more difficult sequel. I wouldn't be surprised if a lot of other people do as well.