I would say that it's a positive if people come away from the experience of watching the movie with greater knowledge of the illness or with some awareness that the person has an illness. However, I just don't see that happening in these movies. The trope seems to play up the character as having desirable behavior that does not come from an illness. The manic pixie dream girl (boy) is usually there to save someone from their humdrum existence. And these characters don't ever seem to have too many consequences for their often bizarre behavior. I've noticed that people come out of these movies thinking that the manic behavior is often a desirable way to behave and not that this person has issues.

I do think that the portrayals are accurate in some of these movies. However, I believe that in real life people would point out that this person is manic and not acting like their baseline selves. Instead it seems in these movies that no one ever points out that the person is behaving in a manic manner. They're just quirky and cute. I think that the trope is just too one dimensional.