I'm always down for Firefight - I think ODST handles it a lot better than Reach in that you always feel like it's a desperate situation with 4 guys holed up in some tiny part of the map, hoping their ammo lasts. GT is OptimusWang.
Well I don't play either regulary but I do still have both and have yet to get all of the achievements. I haven't even finished Gears 2 yet, I guess I should before 3 is out.