I use my Martin Logan Vantages on hard wood floors and I didn't want to ruin the floor with my Mapleshade Threaded Heaveyfeet brass spikes. I made some marble coasters for the speaker feet. Below is a picture. If you want to see the step by step instructions (and more pictures) you can visit the Step by Step Instruction Guide here.

do they work, or do you notice a difference?
i have carpet now and my speakers are on some hand made stands, but if i move i want to setup my
speakers well.

and i don't know what the floors will be next.

I have been able to put a little listening time on the new configuration and I would say that there is a minimal sonic improvement that I notice in the higher frequency range. The low end seems unaffected (as far as I can hear), but the harshness of some of the very high notes seem less, yet more detailed. I would say this is a "modest" improvement at best. It certainly does not degrade the sound. Considering this was a total of a $5 investment, I think it is well worth it. No it won't make $500 speakers sound like $5000 ones, but it will save your floors, look good, and hopefully improve the sound by a bit. I am very happy with the investment vs return ratio.