I was away for the launch of Halo: Reach, but now that I am back I finally had a chance to try it out last night. Co-op is still the most fun experience I ever have with video games. I played for close to three hours last night with my old college room mate and it was the most fun I have had with a game in a long time. Heroic difficulty seems to be well tuned and the new weapons and power-ups have all been really awesome.
And after four iterations of Halo, the pistol is still my favorite gun.