I have a pretty large HRS platform for my big Kuzma turntable. I didn't buy it for isolation, per se, but to have a completely flat surface on which to mount a very heavy turntable and the Airline arm, which needs to be completely level to work properly. It's nicely made and does the job well. As to mechanical isolation from footfalls, it's not terribly effective on its own, the heavy (i mean heavy) old mahogany prayer table that it sits on had to be further isolated to eliminate footfalls. As to isolating from component vibration, I think their stands use the platforms combined with additional decoupling material to make them work.
I had a Finite Elemente stand for a little while for the turntable and it didn't isolate footfalls at all.
I also have a variety of Grand Prix Monaco stands that use the carbon fiber shelfs. I still use those for my line stage and amps. I do remember that they made a significant difference when I placed the equipment on them- but this was 6 years ago, and I haven't tried anything different (other than to replace the little sorbothane pucks).
Taters- I think some people have actually gone back to using a basic, rigid stand, like your Billy Bags, and then adding decoupling, like STillpoints, or other devices under components, rather than using elaborate stands.
I gather that the new STillpoints stand is quite good but I haven't played with it.
I have a huge Billy Bags stand that I bought back in the 90's for my home theatre system, thing is probably 6 feet long and 3 feet high. I am basically willing to give it away when i move so if anybody wants it, PM me. You'll have to pick it up, I ain't shipping it. (And it should probably be bead blasted and powder coated again, I'm sure there's some rust in places, it has been sitting in the pool house).
