I feel the need to say this... Hero or villain is irrelevant to my opinion of him. What is important is that up to a point I supported and was rooting for him. I even supported the idea of his revenge against against those he perceived as having wronged him. However, at a certain point, he went too far. He lost sight of his original goal.
He had the opportunity to make a point, and bring attention to an important issue, but when he went too far, he lost my support.
For the sake of the thread, I'm going to go with "both", as there were definitely elements of both, in my opinion.
If anything, I think it was amusing how far the LAPD went to prove everything he said right in their pursuit of Dorner. Perhaps a better question would be are the LAPD heroes, villains, or both?