Thanks for starting a helpful thread.

I live in a small 2 bdrm apartment and have 3 bikes. I have very little space with all of my other junk.

I can't really mount anything to the walls and I've been looking at those upright racks. My only concern is the stability.

How will it work on carpet?
Does the heavier bike have to go onto the bottom?
Will it stay upright in an earthquake?