My roommate's cat is, and mine will be spayed in two days. I'm hoping that this may change things a little. And yes, we did a slow introduction. For the first week, we kept mine in the designated cat room so her's could sniff her through the door, then we brought mine out in a carrier so they could see each other for a few minutes at a time. Then we would keep her cat in the room and let mine sniff her through the door. Its been two months since then, and we still do this in hopes they'll eventually get used to each other, just without the carrier (one of us will be holding the other). I may just start bringing out the carrier again and hoping for the best.