Personally, I would like the helicopters to either take more damage from small arms fire or include more anti-aircraft options.

I've never played the multiplayer, but I would like more effective golf carts in the single player. Those things are goddamn next to useless. Tanks fuck your shit up.

I'd like the buildings to crumble in more than 1 way.  I'd also like to be able to completely demolish buildings, like in Red Faction Guerrilla.

I'd also like to be able to completely demolish buildings, like in Red Faction Guerrilla. "

" @FrankCanada97: So you're telling me I won't have to spend 30 minutes driving golf carts like a mad man to try and avoid tanks shells while also frantically searching for anti tank ammo? Son of a bitch. "

WAY less traveling in the single player as when your vehicle blows up walking for 30 minutes is not fun. Also a story that isn't so ridiculous

" @kmdrkul: That is confirmed to be in the game, have you seen some of the E3 videos? One clip shows a tank shooting a shell into a house and it collapses. "

 I'd like to be able to drive a tank over terrain without spinning out from hitting a small rock. 

Team chat and not squad only chat.

the game engine maybe.  the console battlefield games have always had weird jerky controls, I hate it.  I can't stand BF1943 because it plays like that too. 

" I would like there to be transport helicopters and parachutes.  "

It seems that they are hinting at more than two multiplayer modes:
From the BF Newsletter:
Q: What kind of online game modes should we expect for Bad Company 2 this year?

A: Battlefield: Bad Company 2 will have Rush, the classic Conquest and the rest will be a pleasant
surprise for everyone. Stay tuned for the details!
– Gordon Van Dyke, Producer
 
Co-op anyone?