IMO, the use of the word "nigga" makes one appear both uneducated and/or immature in about 99% of the instances in which I hear the word used. It's like hearing a white kid from the OC saying "Brah".
Do I think White people should be able to, or want to use the word nigga / nigger? Sure, I'm using them right now. If we're not speaking about the words themselves though, I really have to struggle to see a situation in which the context is appropriate.
Do I think Black people "own" the word. No, but I don't think anyone owns any words. I just listed an example in which I think it's OK for someone who's white to use either nigger or nigga. Do I think a black person has more has more social leniency when using the words in various contexts where a white person couldn’t use the words? Of course, but again, I don’t think that use is doing them any favors outisde of whatever circle they run in where its OK.