I'll agree with Luke on one point, and disagree with him on another.
I have no use whatsoever for rules on romance. They're not needed by me, and I'm not even willing to give them the benefit of a doubt. I don't need game mechanics for human relationships, thanks.
But (PG-13) romance in my game? Sure! Right now there's a PC married to a NPC, and a PC who is in love with another PC, who in turn has just declared love for a third PC. None of it is forced, none of it is weird, and it's making the game more fun -- but none of it is treated as goofy sophmoric humor, either. Because each romance is tied into plot elements, I also find it's adding a whole lot to the quality of the game itself.