Lots of good suggestions here, thanks! For the moment, we have plenty of room for our four bikes in our rather large 2BR apartment, but since we may downsize further eventually (to a 1BR condo), I was getting ideas for the future. Didn't think about the Bike Fridays requiring a different type of mount, but that's a good point - no top tube. We had a couple of hooks to mount them vertically in the garage of the house we just sold and moved from, but they do stick out a lot farther from the wall that way, which may not work in a small space. Will all depend on the particular layout we end up with.

Hanging them from the ceiling (which are typically quite high in the type of condos we're interest in) with pulley systems normally used in garages might be a kind of interesting solution and save wall and floor space. We'd have a lot of patching to do when we wanted to sell the place, tho!

Thanks all!