I recently installed Steam and I see the game Left 4 Dead 2 appear twice, once with a Beta tag and another with the same tag but between parenthesis. Here's a screen capture of what I'm seeing:
What's the difference between these two?
A few days ago I installed the one with the Beta tag in parenthesis and today I purchased the Left 4 Dead + Left 4 Dead 2 bundle (http://store.steampowered.com/sub/2487/) but so far Left 4 Dead 2 hasn't showed up in my Library. Is it the same as the one I already installed? Should I wait a bit more for it to start downloading (it's been ~30 minutes)? This is really confusing.
Left 4 Dead 2 for Linux has not left Beta yet. It is still being tested, as the port to Linux is relatively young.
Left 4 Dead 2 (Beta) is the actual game, while Left 4 Dead 2 Beta is the actual beta (as in: the version that is in active development, as opposed to the port).
Therefore, Left 4 Dead 2 (Beta) is most likely the one you're looking for.