I bought one several years ago when the Acoustic Revive rr-888 came out. It actually made me feel somewhat nauseous when I first started using it. I experimented with placement as well as using a linear power supply.
I have no idea how they actually work or why. I've read material about it as well as Jeff Day's (?) reviews-- I was still left ignorant of what it is actually doing- I think it affects the listener, but some people who I demo'd it to didn't notice a thing.
I still have it, and it is set up if I want to turn it on; I did find that it changed the sound or my perception of the sound, but I'm not sure that I actually preferred the result; it seemed to homogonize the sound and in some ways bring it "in" tighter, taking the raw edge off; but like power conditioners, I wondered if that more "raw" sound without it was providing me with more acoustic information, so I usually leave it off.
Height off the ground is a factor for sure. FWIW, the thing draws so little current-- on the order of hundredths of an amp, at least in the case of the rr-888, I saw no need to continue using a linear supply. (The switching type supply might still interfere with the system so it is on the standard house lines, not the electrical subsystem dedicated to the audio system upstairs).
There were some old threads here that had a lot of posts-- some people used multiple units and really like what it did. I think this is a case of subjective applied voodoo---