Anyone use Mr.Sandless for Hardwood?

sounds like a polymer process ... think car waxes. Traditional wax vs the new polymers which are a new generation of polishes that require less effort to apply and last longer. Basically they act more like a plastic then your old urethane finishes. I would imagine concerns would be about durability (flexibility so it doesn't crack with impacts or movement) and proper adhesion (no separation from the boards or you'd get bubbles).

The other thing is how damaged the existing boards are - these processes typically use a thinner application, so they won't 'fill in' gouges or deep scratches as much as a thicker urethane. So the surface prep is key and of course what your expectations are in regards to obscuring such damage.

I would think if you are just trying to get the shine back - this type of thing is better. But if you are really looking for the resurfacing to get rid of damage, I'd really do some chatting with them inspecting your floor to see what the results would be.

Sanding is slower - but it certainly does much more.