Shoot at the faces of your friends locally in 3D!
Star Fox 64 3D multiplayer is, sadly, local only. The novel thing about the local multiplayer, though, is that the game makes use of the 3DS camera to display you and your opponent's faces above their respective ships. This addition isn't earth-shattering, but it's neat, if a little pointless, effect.
It's a much easier way to find out who's who on the game map, and you can even tap the player's face on the touch screen to turn your ship at them.
The multiplayer also features the gyro controls, and I was somewhat surprised that I used them. As silly as it sounds, Miyamoto was right: you might just instinctively move the system without thinking. For that reason, the gyro controls work as a supplement to the regular controls, much in the same way the gyro controls work as a supplement to the Ocarina of Time 3D controls. I could never imagine using the gyro controls prominently, though.
Aside from those things, Star Fox 64 3D multiplayer is exactly what you'd expect: you pilot Arwings and try to mow down the other players. The graphical enhancements improve the experience, and if you're fortunate enough to have friends nearby with systems and a copy of the game when it comes out on September 11, I envy you. This would likely be fun.