Yeah, more content is a must. Aside from collecting orbs & stunt markers it seems like the game was a little short. I def feel short-changed on the achievements, as I've almost got them all, and won't even get a full 1,000 points for it.
BTW, I got a giddy feeling inside when i booted up the game last night and saw the "New content available" message. I was like, "Is this the content I was asking for? Or maybe the halo 3 beta is available?"...but alas, it was not meant to be. New content was just themes & gamer pix. Oh well...here's waiting.