They released a "demo" of sorts on xbox live.
Its called the initiation station, and it allows you to play with the character creator, after which you can upload your character to the system and use it (or any character uploaded by someone else) in the game when it comes out.
I spent a good hour just tooling around with the creation options. Fun stuff, though there was an interesting option in the body section.
There's a slider called "Sex Appeal". Changing this for a female character predictably makes her rack bigger or smaller. What's funny is that male characters have the option too. It just adjusts something else.
Crank it up to 100 and get some cheap 4th grade laughs as your characters package grows to such a ridiculous size he would surely have trouble walking.
Call me childish, but when I saw that I found it hilarious.