The videos are
here Zofo.
Tbh, I am pretty disappointed now after thinking about it some more.
Imagine if they stopped work on TF2 in April 2008 and announced that TF3 will be released in October 2008. The gameplay videos show
exactly the same game, but 6 new maps (the amount it was originally released with). And that's all.
And TF2 cost only $20. L4D costs $50. People were saying that was too expensive for what it is when it was first released. Now they're giving us the same thing with 4 new campaigns and we have to buy it again.
Even if it was only an expansion pack, I'd be a bit pissed, but that at least would be acceptable. But trying to market this as a new game? And telling us about it when they still haven't even given us the SDK properly? (if they had, then we would have seen more new content than this new game already).
They gave us an unfinished game to start with (didn't even have all the maps playable in versus). I wasn't fooled by that into thinking it was new content. It was a one week job to add some invisible walls, while they were working on L4D2.