Well, it’s here; the official release of Left 4 Dead. If you preordered through Steam, you may have started playing last night at the midnight launch. It’s not too late to get the game today but it is too late to play the demo now.
The demo ended on the official release of the game. There hasn’t been word of whether or not Valve will decide to open the demo again at a later date but for now, if you had the demo downloaded, it will have pre-loaded the game for you. If you try to play, you will get a message that reads “a locked copy of Left 4 Dead Demo has already been installed on your computer. Purchase it now and start playing immediately.”
Left 4 Dead can be purchased through Steam for $49.95. You can learn more about the game at the official site: http://www.l4d.com/
And you can talk about it on the official forums:
This Left 4 Dead information thread is especially helpful if you are new to the game: