The sweep on it's own isn't that great. Combined with not knowing if they may execute the sweep, Lynch is going to run, Wilson is going to run, or Wilson is going to pass is what makes it a useful tool. As others have stated this is only possible because you have a guy talented enough to pull of the sweep, a guy who can be the "point guard" with his decision making and has the ability to pass or run, and probably most importantly a running back who can still beat a defense even when they throw everything at him.
This is a great addition as long as they don't get too cute with it. Unlike the other teams that relied heavily on the read option, Seattle did a really good job of showing the formation while having Wilson take off with it enough to keep the defense occupied, but not enough for them to key on it and beat him down. When they used it last year, it looked great out of regular running plays, regular passing plays, and play action.
When you think about how they're accomplishing this with a running back that was a demoted castoff, a quarterback who few thought would be a starter, and a receiver with a weird past it's amazing just like it is building a top defense the same way.