I have seen him playing since he was a child, and he is the most talented SF (Talent wise) that Spain has ever had. That said, he has serious confidence issues. He was the starting SF for Spain at the initial games, but there were many situations where he should take a shot and he would pass the ball being open.
He has all the tools to be a star in Europe, for his size he is probably one of the most athletic guys playing in Europe if not the most, can handle the ball, is very coordinate for a guy of his size. He is a good passer, great shooter... Can play some PF, but in the nba due to his lack of bulk he is a clear cut SF. Defensively, he is not a mess but has to improve a lot and be more active, can block some shots when focus on defense.
He is an all-around player. His ceiling is a more athletic, quicker version of Rashard Lewis, but that´s gonna be very complicated reach.
He was playing the best basketball of his life at the beginning of this season but then he had a hard injury on his knee and stayed out of the game for 5 months or so. He will stay in Spain for two more years at least, and that situation will do wonders for him, because he will get used to be the main guy on Pamesa Valencia.
Regarding Portland they may have drafted a SF version of Rudy Fernandez if he solves that confidence issues and keeps developing, high risk-high reward kind of situation because he may not pan out and be just a 3point threat coming from the bench in the nba.
If he pans out he is a starting SF in the NBA and a 15ppg man in the right situation.
That video sums up his skill set:
http://www.youtube.com/watch?v=DhSmBuB81tg