I'm just watching GTTV, and there was an interview with a higher-up at Valve (not Gabe Newell), and they were showing off the zombie side for the first time in a long time.  The only new detail that really caught my ear was that he said players will be switching sides between rounds of a campaign.  So, if you're a human in the first round, you'll be a zombie next.

I hope that's optional, as I'd like to have the unified feeling of either guiding a character through this terrible situation, or endlessly stalking them Nemesis-style

You might be able to set that option, but it sounds like that will be the norm.

Rest assured the campaign mode you'll be survivor all the time, no switching or anything...Versus mode is a bit different I guess.

Also, HOLY CRAP I need to see this video! GameTrailers is supposed to post it! I didn't know it was on TV already.

Playing as a zombie has never been shown in all my months of waiting.

The video wasn't that interesting--only a few seconds of boss gameplay, with the rest mostly being from the human perspective we've seen so many times before. Also, I saw zombie footage on IGN months ago.

There is no difference between Campaign and Versus--it'll be similar in that way to Perfect Dark's Counter-Operative mode, where it's the same continuous campaign with enemy players controlling the enemies.

Just play co-op without any human zombie players.

thekitchensink said: The video wasn't that interesting--only a few seconds of boss gameplay, with the rest mostly being from the human perspective we've seen so many times before. Also, I saw zombie footage on IGN months ago. There is no difference between Campaign and Versus--it'll be similar in that way to Perfect Dark's Counter-Operative mode, where it's the same continuous campaign with enemy players controlling the enemies.

No, there is a difference between Campaign and Versus.  In Campaign mode, the AI Director makes your game smooth...with crazy intense parts and slower scary parts.

The Director makes Versus all crazy all the time, so it's much harder for the Survivors.  I'm guessing that will make the games shorter.