Some of you may have noticed already, but I posted the .ccgame of my entry of insane game to the dream build play competition here: http://forums.xna.com/forums/t/17876.aspx.
For those who saw an earlier version of it at the show&tell, I managed to speed up the terrain generation on the 360 in the end, and it DID involve generating the procedural texture on the graphics card :P
The 360 cpu really does seem to have problems in xna. There's still some stuff I can shift over or precalculate, but it's certainly very playable now with terrain on.
I was going to release a windows version especially for you guys, but I got a bit carried away trying to add AI and so didn't get round to packaging a solid version before disappearing to find a flat in cambridge (I'm still there now).
Post about it here and on the xna forum if you have any comments, thanks :)