I got it yesterday from Sweetwater. They are really trying to make sure their CS is good, I got a phone call asking about how I was going to use the stand, and an offer to call or email if needed. Shipping was same-day, and they threw in a little bag of candies.
The top and bottom platforms are made out of heavy plastic, seems thick and durable enough for it's intended purpose. Each corner of the platforms has a rubber insert. On top and bottom, the insert forms a rubber foot to contact the floor and subwoofer. In the middle the rubber cups accept 4" long steel tubes that join the top and bottom platforms into one unit.
The rubber inserts allow the cabinet to "float" and has quite a bit of compliance in the horizontal plane. A light touch is enough to move the cabinet visibly. There is some vertical compliance as well, but much less than in the horizontal direction.
So, this stand is seems like it will do a better job of decoupling the speaker than a foam platform, and by quite a bit. For me, it makes more sense to firmly couple a subwoofer cabinet to the floor, but it's pretty obvious this is back-assward when tested out. The box says it allows float which gets rid of resonances, and it when you listen it's pretty obvious this is happening and the results are better than a coupled cabinet.
Generally with these things if I don't notice a difference right away it's not significant enough for me to worry about, but I can say it made a difference and didn't require a careful A/B either. The result is cleaner sounding bass, simple as that. I do think the results will vary depending on your equipment, but with my simple 10" sealed subwoofer it was definitely worth it.
I was just thinking with a downfiring sub you could put a platform on the stand that the sub would sit on, but that would change other things too... maybe for the better, maybe not.
edit: dimensions are 8 x 10" or 6 x 8" between center of supports. They support 75 lbs, but you can use 2 of them for larger subs.
The improvement in bass translates to better clarity and detail in the rest of the frequency spectrum as well. We have all experienced how good bass elevates the sound of a system, this is no different and the change is very noticeable.
edit2: I am going to have to order a pair for my speaker stands. I have low stands currently on brass spikes, but the spikes are sitting on pennies with thick felt underneath to decouple from my hardwood floor. I am going to replace the brass spikes with these devices, the monitor ones are 3 or 8" tall. Or I could get 2 subwoofer platforms for the same price as a pair of mediums since I will not raise or tilt the devices...
In any case, I think isol8r is going to sell a lot of these things!