The instincts editor was fairly easy to use, the skill was in using the bits to make more original structures. For instance the best map I ever made was a quarry, lots of broken machines and stuff at the bottom with a spiral track going around it. I used the round fort type buildings to make bunkers, old rusty tanks with bits added on to make diggers. Even with all those blocks, I think that using them in interesting ways will be the order of the day.
At the end of the video, the level looks a lot like a BF2 map, if we can get that complex with them then it will be a whole new XBL sport.