I've got it installed too. I'm not as jealous as I would be a couple of days ago.
But recently I played some too. only it was not on steam, we have media convention going on (Armageddon expo) so I've been playing it on the xbox at the EA booth. It's a bit harder to do stuff on the 360, but it's great fun. The boomer bile grenade is actually really cool, pretty useful in a way I wouldn't have expected, being there were no videos of it in action and I had only the boomer mechanics to guess at. Special infected all look twice as creepy (particularly the female boomer. squick.) and although the content appeared limited in the demo (only about four melee weapons and a half dozen guns), it was still great fun to go through the New Orleans streets with a machete.
Speaking of which, did you notice them changing? I actually spotted on a second playthrough a fence that had been erected over the route I had gone last time.
I can't wait.
I assume you know the details of all the things I'm talking about if indeed it isn't a sneaky photoshop job/sourcemod with the same name.
I wonder if I can ask Valve about it given I've played it a bit already? I might do that.