It is really interesting to see if Beckham will have any influence. This is not the first time that prominent imports (who were, ahem, past their prime) have tried to popularize soccer in the US. Previous stars who played here include George Best, Pele, and Klinsmann, among others.
It was a little before my time, but I'm told that there were no restrictions on big-name players then? Apparently The Cosmos and The Aztecs just bought everyone and every other team suffered.
This new 'one big player' rule should stop that hopefully.
I've heard good things about the MLS. I don't think Iain Macintosh has been particularly fair in referring to it as a place for, "35 year olds with wobbly knees".