I don't think Joni misses going outside much. She's not a particularly large or assertive cat, so other cats might have been a bit of a worry. She never went out for long, or seemed to go very far (except a few times when, endearingly, she followed our son a long way to make sure he was all right).
That said, she was very, very interested in this pigeon on our balcony.
(Too bad, Joni. It's seventeen floors up and you're not going out there.)