I find "lover" kind of an unpleasant word in most contexts, because it seems unnecessarily specific. It's like you're saying "the person I have sex with" every time you refer to them -- TMI. It also implies a non-committed relationship to me.

But I like "partner" a lot. It's a nice word, implying commitment, fairly neutral between gay and straight, not overtly sexual.

The trouble in fic is usually not the choice of words, but the excessive use of the same epithets over and over in place of a character's name. Unless you're writing about Voldemort (or unless your name is Homer), that's not good style.