What do you think Adu's biggest weakness on the field is going to be? Will he have a difficult time with experienced defenders?
One thing that I think made Adu's (and his mom's) decision to sign with MLS easy is the fact that he WON'T be playing against the most experienced defenders in the world. Not that he'll be facing chopped liver, or that he'd be starting every game in Serie A, but it's safe to say that he has the chance to stand out more quickly and easily in MLS than in one of the bigger leagues. Pair that with a better overall standard of living than he'd find in some other league where he would be starting and suddenly the US of A looks like a soccer haven.
Adu's weaknesses, from what I've seen, have all to do with game experience and offensive strategy. TONS of young players have that problem, and it's almost a global epidmic in finding quality players who know how to build a team attack. He reads the game flow very well (why I suspect he's not 14), but now he has to be part of a team strategy and understand that his opponents will have planned to counter that. He's not sneaking up on anyone, anymore.
His physical toughness will need some work, too, but that will come. Faster defenders will body up on him a lot, knowing that for every time young Adu gets past them, there'll be other times where he'll be timid, weak, or prone to dribble into trouble while trying to escape one man. He did this several times while playing on the U-17 squad. I don't know if he's ready for professional fouls on a regular basis, or if the league and team will protect him like a star QB.
Adu is quite simply someone with great vision, speed and ball control skills for someone his age, even if he is 16 or 18. I'd put him somewhere between Kirovski and Beasley in talent, with slightly more imaginative/ aggressive dribbling skills. If he stays within his limits for now, he'll learn a great deal about game play and can take over more and more while applying those new skills in practice first and in the games second. A lot depends on what he wants to play, too. Too much time at the forward position and you get Van Nistelrooy (Captain One-Dimensional!!), whereas not enough time in the attack and you get a disgruntled Valderrama ("Win, shmin! Look at these moves!!") ;D
Keep in mind United is still "rebuilding," too. No Etcheverry, new coach, limited offense. They'll ride a lot of enthusiastic support from the fans coming to watch the wonderkid, but that could work against them if the team struggles early and often against a league where they're maybe the 6 or 7th best out of ten teams.
Then again, there's a lot of time for the guy to grow, and I'm just one man at a desk south of Atlanta. Sorry for the long windedness: I just love talking soccer! Enjoy the games for me, sir, as I'm too far and too booked to see any in person this year. :'(