He was supposed to be great and he certainly has talent still to be a hell of a player. From age 14-18 he really didn't get any better they were like lost years. Probaly should have headed for a European academy at around 16 where he would have gotten into reserve team matches and had better coaches. Alot of it was his own fault MLS he got a big head and didn't really try to get better. Blamed the coach for sitting him when in fact he wasn't good enough to start in the MLS. Partied alot too. However getting shipped to Salt Lake seemed to give him a wake up call. And is supposedly training hard.
I don't think he's doing too bad at Benfica. His problem was that the coach who bought him got fired a few days after signing him. According to Wiki He has a scored 5 goals in 14 matches and is currently only used as a sub (1 start). He's playing as an attacking midfielder (not sure on the wing or central midfield) when his ideal position is probaly as a playmaking striker on the wing in a 4-3-3. If he's playing central midfield he'll struggle. His passing in the middle of the pitch isn't very good and center halves and holding midfielders gang up on him rough him up. He does most of his damage on the wing and can get by almost anyone 1 on 1. Plus he's an excellent crosser. I had my doubts about the guy but when I saw him a couple times at the U-20 World Cup only Aguero was better. However he was the most exciting player in the competition.
Not sure if he'll be a good Prem player. I think he would need a couple years for him to adjust to the physicality of the league. Veteran physical players always knocked him off his game in the MLS. Any prem team that gets him will have to have patience. If he does become good/great I don't think you will see it until around his 25th birthday.
Striker is a serious weakness for the US team. However if Freddy and Altidore develop quickly the US isn't going to be an easy out. If all goes well the US may be one of the favorites in the World cup in 2014 and 2018.
Best case senario?: Pre Real Madrid Robinho or maybe Rosicky.
Worst case: Ji Sun-Park. A decent backup.