...we didn’t sit down and say, “We need to ship a sequel next for next Christmas, what features do we need?” That wasn’t the way it happened, that’s not the way Valve works. What did happen was, the team sat down and said, “We’ve got a bunch of ideas of stuff we want to do.”...So we put a lot of those things on the board and said, “What can we do quickly? What’s going to take more time? What’s the best way to get stuff out to customers?” And part of that plan ended up with L4D2, with things like changing the way the finales worked, introducing some new Survivors, giving new dialogue, telling more about the story, introducing new Specials. We said, “Wow, that makes for a nice sequel.”
You can read the whole thing here.
Eurogamer have gone hands on with L4D2, you can read their impressions here.
