I love using the term "lover" to refer to the people I'm in relationships with. For me, this doesn't have the connotation of illicitness, though I know for many people it does. To me, a "lover" is someone I love, someone I make love with, and someone who has a more special relationship with me than just a friend.
In casual conversation I might call someone my sweetie or my boyfriend/girlfriend, and in mixed (poly/mono that is) company or when I'm being "formal", I simply call them my partners. All of them. (I do have a husband, by the way, but as we don't live together anymore that term is quite misleading.)