Looks like I get to blow my first post in escapist forums on this thread (pleasedon'thurtme)
I bought L4D maybe 3 months after it was released, played mainly campaign until another 2 months - because versus gave me the impression of griefing hilarity (and mainly because I'm a girly pansy), and loved it ever since. Even if Valve's trying to pull this crap on the general populace so early in an attempt to rake in more money, it's got me sold.
I guess it's a little like Nintendo - they're so popular they can slap their logo on a fork and sell it for over a grand (alright, I might be exaggerating there just a little bit, but I've got both the DS lite and a Wii at home, so go figure). If Valve keeps churning out awesome games like this, I don't care how fast they come. Just as long as I have my hot little hands on their copy of L4D2 within a month or 2 after its release, I'll die (semi)happy. I can't wait to try out the chainsaw.
That other thing being I've never really played any of the half-life series, so I'm far too ignorant as to why it should come out before L4D2, which in my oblivious opinion is far better than any single-player shooter.
*Waits for angry posts?*