OCs and other good things in life...
I like OCs, and I don't suppose there are too many of them. I feel about OCs as I feel about any fiction writing--as long as they are good characters, written well, they're a good thing.
OCs give writers a chance to develop a character from scratch, which is really important, especially if the writer does more than fan fiction. And I think there are many of us who write much more than fan fiction. You have to learn to balance traits, build in strengths and weakenesses, and launch a character as a real person. You have to make them into someone who acts up and refuses to work with you if you try to make him or her do something that's not in their personality. (Ever tried to explain that to a non-writing friend? Had one of those conversations? "I can't get my character to just walk into the store and shout at her boyfriend." "Well, why not? It's your character. You can make her do whatever you want." "Well, no, actually, I can't." Yeah. And your non-writing friend gives you that look. And you mumble something about going to look for your marbles, and you try to mark the incident in your mind so you don't talk about characters to that person ever again.)
In some ways, I almost feel a little guilty if I try to write much that is strictly from the POV of a cannon character. I kind of have a feeling that they, especially Harry, belong to JKR. But that's a "me" thing. I don't think anybody else should have any discomfort using a cannon character. Who knows--maybe in time I'll even get over this and produce a really fantastic fanfic with Harry front and center!
Hmm. Then again, maybe not.
Anyway--I like OCs. :D