Yeah that's a really bad thing they did, I don't know why they even did it. They didn't do that with the TF2 demo did they? It's ridiculous, I really do hope they fix that.
I am really interested in how versus mode is. I don't know why they didn't include that in the demo. It feels weird that PC users basically get something that feels like it was from the Xbox live marketplace. It feels like Valve didn't want to short change the 360 owners, so they cut out stuff for us PC users since demos on the marketplace never have the full content. The whole experience feels very consolish, I don't remember TF2 doing that at all.
But the game is very enjoyable, especially with friends. It's a shame there isn't enough content to really get a grasp of how good things could be.