I think it's a lot more than just stride length that gives him an advantage.
With four more years until the London Olympics, which is his ultimate goal, I can guarantee he will make drastic improvements as he improves his "blades" now that he's been declare eligible to compete.
Like someone has pointed out before, based on studies of his "blades" I've seen, if he moves up to the 800 meters he will be unstoppable. Nobody would be able to stay with him the final 200 meters.
As for the 400, he'll most likely be an alternate at this year's Olympics and get tons of media coverage, then by 2012 he will be at the top. It would be good as far as drawing in more fans, but a disaster as far as track and field goes.
Hopefully the ruling is changed as more studies come out.