Click screencap to view. It's ~3 minutes.
I expect this to be on Steam soon enough.
I'm not going to lie, with all the new crap Valve has been showing off (actual ingame features, that is), Left 4 Dead 2 is looking pretty fucking awesome-- A lot better than the original (though I still feel the original characters were leagues better than these new guys). I just wish I knew this was coming from the beginning. The only thing keeping me on the fence about buying it at this point is that I already spent $45 on the original.
Edit: And fuck, whatever happened to the L4D SDK anyway?!