There is another thread right below this one about ODST. So far I like it. If you just run through all of the missions, the whole game doesn't take very long to beat, but I'm taking my time and trying to find all of the audio logs and get all of the achievements that I can on my first run, so it's taking me a little while.
Firefight is fun, though I haven't had the pleasure of doing the full 4 player with it yet.
One of the things that I find kind of dumb is that on the second disc that has all of the Halo 3 multiplayer maps, you can't just install the maps like you would when you buy the map packs. You have to run the disc to get the 3 new maps. It's not a problem if all you play is Halo 3 multiplayer, but if you like to play the campaign, then you have to switch back to the original Halo 3 disc when you want to do that, then switch back to the other disc for multi-player.
