I've only heard people say he's a great talent but an underachiever thus far because he doesn't have his head on straight. I've not heard one non-homer Cowboys fan say he was a top 10 wideout.
You have to be rated higher than what you actual are to be overrated. He's what he is at this point, a great talent...a borderline top 5 talent in the NFL at WR who still has a lot of fine tuning to do. He's still 23 years old.
I wouldn't be surprised at all if in two-three years he's firmly inside the top 10 for WR's. I actually expect that.