I just jumped from a crop sensor (Canon XSi) to full frame (Canon 6D). Wow. Some of the improvement was from moving from an older camera to a newer one, but not all. The low light shots I can get now are amazing. But I am shooting indoor sports also, see below. I never could have captured this image on my old camera. With a new crop sensor (Canon 70D, my second choice), I probably would captured a very similar image, but would not also have the amazing low light performance. My personal belief is that the market will move toward full frame on DSLRs as the cost of producing the FF sensor comes down. The crop sensors were just a stop-gap measure to lower the cost. Other than shooting wildlife, there really isn't a great reason to have all your lenses shoot at a different focal length than displayed.
