I dug up from nbadraft.net comments by a European scout, Borko Popic, about Gallo. The comments are dated June 17, 2008, which I believe was just prior to the draft and when Gallo was still 19..
These are the comments concerning Gallo's weaknesses:
"A high level European player does not always equal a contributor in the NBA, His body has a ways to go before it will be on the NBA level. Athleticism and explosiveness are just average. Struggles dribbling the ball against physical defenders which hurts even more considering his blow by ability is limited. His secondary moves off the dribble are subpar and he is often forced to shoot offbalance shots. Tends to dribble the ball high and even looks down on it as he is attacking, hurting his court vision and decision making. Has minimal elevation on his jump shot, he is more of a set shooter and his release is very robotic and lacks fluidness. His legs are stiff which makes his movements seem a bit awkward and it takes away from his quickness. While he has good height, he is strictly a perimeter player as he has minimal back to the basket moves and his weak frame also makes him a non threat in the post. His rebounding numbers are only decent for a player in his position getting major minutes. They should be higher. Defensively he is a liability, he gambles too much, plays with his hands down and is undisciplined. Marginal foot speed and a weak body will leave his opponents salivating in excitement to abuse the mismatch."
These are two year old comments. I think Gallo's shot is plenty fluid now, but otherwise the comments are spot on even today. I think he has gotten much better defensively, but there is a lot of current truth to these two year objections about Gallo's capacities.
I remain a believer that with some serious training and physical development in the off season he will improve. But it is going to take an awful lot of improvement to come close to justifying passing on Lopez.