Valve have certainly had a good run as being one of the bastions of happiness and light for PC gamers. Their post-release commitment to their games (particularly TF2, which has been updated numerous times over the past 18 months with new features and bugfixes) is one that many companies should envy.
At E3 last week though they managed to shoot themselves in the foot somewhat and undo a little of this good work by announcing Left 4 Dead 2 barely 6 months after the release of the first game and its scheduled release one year from the release of the first game.
First off I'll be amazed if they manage to stick to this release date, as Valve is notoriously fickle about releases, preferring to hold them "until it's done" rather than stick to some arbitrary date. Yet the fast-track on the release may also be a problem in itself. The detractors of L4D 2 argue that much (most?) of its content is lifted straight from the original game, meaning Valve do not have to start this process from scratch. New AI Director? Well it's going to be a modified version of the first. The overall game engine? Again, a modified version of the original game's Source engine. New characters, weapons, zombies? Most of the work has already been done in the first game and so the new stuff can be added in to L4D 2 with only relatively minor adjustments needed.
Critics also argue that releasing a sequel so soon after the original game will cannibalise the community of the first game, both the public community and any updates from Valve for the original game (as their focus will now shift to the sequel). They point to how Valve have treated Team Fortress 2 as the standard of how things should be approached, which has released major content patches for the majority of the classes available and is still being updated regularly today. They argue that L4D 2 should instead be downloadable content for the original game and not a full blown (and more importantly, full-priced) sequel in its own right.
I do think Valve have made a bit of a mess of this one, and it's unusual because Valve can usually do no wrong. Along with Blizzard they are really one of those developers who seem to put the gamer first ahead of any other considerations. They do not rush games out the door (usually...) and release them when they are 100% satisfied with the product. Case in point: Half-Life 2 Episode 3 is completely MIA with no new information about it released at all, even at E3. I can only assume that this is because they are still working on it and it's not in a good enough state for them to want to show the public (or the press) at this point.
But back to L4D 2, I think you will see some kind of announcement soon by Valve addressing this issue. It may take the form of a discount on the price of L4D 2 for original L4D owners; it may be a changing from a full retail game to downloadable content for the original game, it may even be a cheaper full-blown expansion. Either way I don't think Valve will let things go on as they are. They have made a very profitable empire out of giving complete satisfaction to gamers and know that the current controversy is giving them negative press which they are unaccustomed to. From their actions in the past I suspect they will work to correct the situation and we will be hearing something very soon about it all.
In the meantime, check out this video made by the anti-L4D 2 community: