Good maps, useful duals, no lasers, dual needlers, a shotgun that isn't a camping tool, the round thing on the side of a ghost that is a one-hit kill, a gauss hog that isn't overpowered, a better version of Land Grab, awesome maps, little/no lag, even in BTB, easier to find games in, even with the small population, fewer annoying little kids, great maps, actual Covie weapon maps, better Brute Shot, realistic turrets, the Spectre.
Oh, and did I mention the maps?