It really is a complex issue. I have Asperger's syndrome myself, and while I'm on the very borderline of being considered for that (it is on a scale after all), it still clearly impacts my life. For those with more extreme Autism, it can affect their life even more.

Most important is that Autism itself though is just a condition like any other. It varies a lot based on the individual, and you need to make sure that when you portray a character with Autism that you are making them an actual character.

Just as if you wrote someone with a physical handicap that you shouldn't define them just by that, or if you wrote someone with any other condition that makes living life more difficult. Which no doubt Autism does - it wouldn't be considered a condition if it had no negative effects - but that doesn't stop those with Autism from living perfectly fulfilling lives.