The game needs gamepad support. Xbox 360 controller support is a given but PS3 controller support would be awesome! Generic gamepads should be allowed too. Not everyone enjoys the keyboard/mouse setup afterall.
The game, even after release should remain completely free, if that's the route they are trying to go down with it.. Paid-content will only provide unfair advantages to some while leaving the majority out and will likely only decrease the number of players overall down the road, which will kill the game sooner than is needed.
Player matchmaking needs a bit of work. Most matches are fairly one-sided and the winning team is usually determined before the match even starts based on major stat differences.
I'm sure some of these have probably been suggested already but these are just a few that are really important to me.