He's an entertainer, not a scientist. His stuff is definitely entertaining and thought provoking, but he does make some "Gladwellian leaps" to gloss over some inconvenient facts to get to his ideas.
10K hours part is good example where people just jump on him for making this bullshit theory about anyone becoming expert by putting mindless 10,000 hours in any skill one wanted to acquire. But reading that book I never got impression that it is some kind of magic.
What I find most funny is that a lot of people who find MG fraud can easily get hoodwinked with some other person/place/technology/thing if they just happen to like it.