Euphemisms aside, I hope the little information I can provide proves helpful for some folks. If you're unfamiliar with the PMS, it's just a way to mount your pickups (specifically humbuckers, I have no idea if these are at all compatible with single-coil pickups).
The idea presented on FU-Tone's website is similar to what some folks have said about direct-mounting pickups for years. 'The REAL voice of your instrument.' 'Better tone.' And other such statements of questionable validity.
The PMS itself is simply a well-milled hunk of bell brass with five holes in it. Two for mounting to the body of the guitar, two for the pickup leg adjustment screws and one big one in the middle for a larger screw that sets the pickup height. Installation is ... relatively simple. It does require you to make a few measurements to get your pickup positioned correctly and there is some test fitting involved (or at least there should be) before the whole apparatus is affixed to your guitar. But once you have everything adjusted the way you like it and your guitar is tuned and ready to play... what difference does it make?
Here comes the fun part. Did it change the way my guitar sounds much? Not significantly. I'd guess somewhere in the 5-7% range (it seems just a tiny bit more full sounding and has a hair more sustain to my ears). Folks can debate the merits of different materials/methods till they're blue in the face, but not everything works for every player. I imagine there are some players who installed the PMS and it altered the sonic qualities of their instrument enough to make it amazing for them. Then there are folks like myself who really don't hear much of a difference at all. Why I enjoy the PMS is because it provides IMHO a more sturdy connection between the pickup and the guitar (I tend to enjoy things that are over-built).
Happy modifications to all and I hope the day finds you well.