I'd love to take your bet about Demps vs Rainey. See, he isn't just a top speed guy. Care to guess who won the NCAA indoor 60m title? That's got a lot more to do with acceleration than top speed. It's swell that Rainey was able to pull one off him once, no doubt the kid's got wheels, but that's kind of a blind squirrel and a nut kinda thing.
Actually the only thing that ever needed squared, with me anyway, is this insane idea that Young is, y'know, sorta-kinda-not slow in your eyes. That's simply not accurate. In the 2010 track season there were exactly two people in the entire state of TN that managed to officially go under 10.80 twice...Travis Thornhill and Devrin Young. That's it, that's all.
As for how good an actual football player he'll turn out to be at this level...hell if I know. I just wish people would get over this idea that he isn't plenty, and I do mean plenty fast enough to play at this level.
As for the Byrd issue it's really simple, one place was "slow" (remember, a 4.55 was the fastest anybody ran at that combine) vs some places where times run to the fast side. It's why hs/college 40 times are nigh impossible to compare and the NFL tries to get everybody to run at the same place to keep it as apples to apples as they can manage.