So it was announced that this game will support 3D on PC, PS3 and 360.. I am aware of PCs and PS3s implementation of 3D, but how will it work on 360? does the 360 support that stuff yet or will it be relying on the TV to make it work..?

Its too soon to say what tech they are using but the 360 is capable of doing 3D. Some games released in 3D on the 360 (Batman Arkham Asylum Game of the year edition and a couple others). I think they will be using the same tech but most prob more improved. I'm sure we will find out closer to the release date.

The 360 has supported 3D longer than the PS3 has I think. MS just doesn't talk about it because there is no real benefit in it for them other then making sure their platform supports it so they can have feature parity.

I don't know what's more gimmicky: motion controls or 3D TV's.

There is nothing special about the hardware of the PS3 allowing 3D, it's all done within the software, and the 360 will do it in the same way. The only reason 3D has been big on the PS3 is because Sony have been pushing it because of their investment in 3D TV's.