Harvin is a huge talent who scores touchdowns but I have to echo what Crazy said. Why would they trade him? I don't really buy it.
The biggest issue with Harvin is not the migranes. Before this year he'd only missed three games in three years. It's his personality, which has always been, let's say, temperamental. If Philbin was on board shipping a guy like Marshall out of town I can't imagine him pounding the table to bring Harvin here.
Then there's the question of whether we even really know how to use him. Reggie Bush has some of the same versatility you find in Percy Harvin yet we barely exploited it. If you stick Percy Harvin out on the perimeter to run skinny posts all game long you're misusing him, yet based on the way we used Bush why should I imagine we'd do anything else?
All in all I'd rather find a way to end up with Steadman Bailey or a Tavon Austin if this is the kind of thing you're looking for.
read the link and you will see why... he is in the final year of his contract and wants out... he could be used like Randall Cobb for GB in the slot, out wide, at runningback although they played Tavon some at RB in college he is too little to do so in pros..