I'm checking out the IGN video right now, for those who don't want to download the massive file, here are the Balloon Battle tracks. If you can, its worth checking out. I guess this is a spoiler...
BALLOON BATTLE
Nintendo DS
Twilight House
Palm Shore
Tart Top
Block Fort (CLASSIC AWESOME BATTLE TRACK!!!!!!!!!)
Pipe Plaza (MK

D classic track)
Other Balloon Battle notes:
- You start out with only 4 balloons, but only one is inflated. To inflate the other 3, you have to blow in the microphone. I am not kidding, and you'll look like a fool in public doing this. The other option is to press select repeatedly, but that works slowly.
- Balloon stealing boost from MK;DD is back.
- There is a vs. CPU mode.
Shine Runners mode:
- Race to find shines on the battle mode stages
- Shines appear on BOTH screens, so you can use the touch screen as a map to find shines
- Hit other players, and they lose shines (duh)
- There's a clock that counts down, and at the end of each interval, two players get booted
- Looks like a max of 8 players can play this mode.
- Second screen also shows how many shines each player has, and the item that they are currently holding.
Mission Mode:
- There are six levels of missions available, and nine missions in the level that the demo shows. So if thats the case for all levels, there should be 54 missions.
- Boss battles are included, and they looked great.