If you assemble the mobile correctly, it hangs perfectly and moves slowly from any air currents in the room. We hung ours over our dining room table and it looks awesome.

I have this mobile - for my son's crib - and he ADORES it! However, it doesn't hang the way it's shown here. the second to bottom piece (the last one-sided) hangs at a 45 degree angle instead of parallel to all the other pieces. Not sure why... something wrong with the weighting? At any rate, it looks great, just doesn't work as well because the piece in question knocks into other pieces instead of allowing all to move freely.