In no particular order:
The parkour. While I may end up doing a lot of the “auto” parkouring, I look forward to watching the skilled players manually slidin’, gliding’, and flyin’ through the geometry.
The team-oriented gameplay. First, this is a genuine class-based game, not just some weapon “loadout” stuff. Second, Splash Damage is putting their money where their mouth is. Rewarding team promoting actions.
Something for everyone via the classes.
A visual feast for the eyes. I really look forward to seeing the individuality of each gamer come out as they choose their custom skin. Seein’ my buddies all pimped out in whatever floats their boat is gonna be fun!
Little things. It will have story-telling collectibles. It will have XP and continual unlocks and upgrades.
The room will always, always be “full”. Bots are usually just tacked on, but not here. SD has designed them into the game from the beginning, and I believe they will provide sufficiently entertaining adversaries for those times when the room didn’t quite fill up, or when the room needed to be emptied of Griefers.
Splash Damage play their game. I am expecting a level of polish, balance, and stability that many games made by developers that don’t play them, don’t have.
It’s fresh and innovative. BF:BC2, L4D(2), and Gears of War have taught me that even if a game isn’t perfect, if it brings something new to the table, provides good reason for gamers to cooperate with each other, and rewards a variety of gameplay styles, the net result is even more than the sum of its parts.
I am hoping that this becomes a staple for gaming for years.