first of all, we need to differentiate here. I heard a comedian once say that pronouncing the ER will put you in the ER. I feel the same way. i would never say the word nigger casually.
as far as the word nigga is concerned, i used to say it whenever id be drinkin or whatever, it kinda comes out naturally when you listen to wayy too much nas. but i dont really say it anymore. I feel too self-consious when i do it, like when you're about to cuss around your parents. i use substitutes like fella or pimpin or plurrr. some people say brutha but i dont. i'll say bruh but not brutha. i do sometimes refer to black men as brothas though, or black women as sistas.
bottom line is, i get annoyed when i hear white boys say it, so i dont say it.
for q-tip's opinion listen to sucka nigga from midnight marauders