My experience has been yes for interconnects; haven't noticed much difference with speaker cables, but the risers do keep them much tidier. I ran my interconnects under my floor and suspended them as Geoffkait mentions from the basement ceiling (we used rubber bands and a silicone gel), it did make quite a difference in sound quality (especially in smearing of images) vs. having them on the floor. I don't think you need to spend a fortune on the things, but they can help.
