I'm looking forward to it too. I haven't got the demo, but it looks great. I hope its better than Halo 2. Still haven't completed Halo 2 yet. The side missions as a alien thing was gay, I hope they get shot of that part.
Most people I've played with really like it. I like the ability to veto a game if you don't like the gametype. I only have a little bit of lag when I use the man cannon (but that's only because I've got a sh*t connection). I really like the assault rifle from Halo 1, and the new weapons I've used are the spartan laser, land mine, bubble shield, portable air lift, these guns which are like smg's sorta and the spike grenades. There's also the mongoose which is cool to hoon around in.