Has anyone had experiences good or bad with speaker isolation or isolation in general ?

Almost all of the current vibration isolation devices, yes, including mine (the exception is the Minus K platform that gets down to sub Hertz performance). By performance I refer to the device’s resonant frequency under load. But wait! Resonant frequency is not where isolation occurs, it’s where the low pass filter characteristic starts. The real point where isolation occurs, or I should say STARTS TO OCCUR, for a particular direction is actually around 2 times the Fr. Thus for an iso device with Fr of 3Hz the isolation begins at around 6Hz. And even then the percentage of isolation effectiveness is quite low at 6Hz, maybe around 10% and at 10Hz maybe 30%. Robust isolation won’t occur until at least 20Hz, where effectiveness is around 95%. Above 20Hz effectiveness approaches 100% as frequency rises.

So, here’s the problem with almost all of the current batch of iso devices - they don’t go low enough to actually deal with much of the seismic energy produced by the Earth crust motion, traffic, subways, wind and other things which lies in the region 0 to 10Hz. And the main reason why the Fr of these iso devices cannot get down below 3Hz is because so many springs are required for stability. The spring rate for the device is calculated by multiplying the spring rate of one spring by the number of (steel or air spring) springs required, which is usually 3 or 4. The Fr of the device is the square root of the total Spring Rate divided by the total mass on the springs including any ballast (e.g., Vibraplane) and mass of top plate.

The Minus K achieves a sub Hertz Fr because it’s a much more complicated design (negative stiffness) than a relatively simple mass on spring like just about every other platform or stand. My Nimbus Sub Hertz platform of yore, sorry no longer available, achieved 0.5 Hz Fr in some directions because it used a single air spring. This single air spring design is almost impossible to construct because a single air spring is very floppy, so it’s like trying to balance yourself on a rubber pole. And it was limited to how much load it could isolate. But it could easily isolate about 35 lb. With sub Hetz performance now you’re talking some serious isolation effectiveness compared to the 3 Hz crowd. As I recall my spring based Promethean Base and the current mini Isolators can achieve around 2 Hz performance if you play your cards right. And my Nirvana dual layer design can get very close to sub Hertz performance, using two stages of heavy masses and springs.

@geoffkait of course another solution for proper seismic isolation is an active platform. These solutions offer 90% at 3Hz and 99% at 10Hz which is enough to make a meaningful difference in the range of interest. Of course they are a little expensive but dealing with this range (say 2-20Hz) is going to cost.

Illustrative data sheet and performance
http://www.herzan.com/wp-content/uploads/2015/12/TS-Series-Data-Sheet.pdf

Folkfreak wrote,

"Of course they are a little more expensive."

I’d opine beyond the means of most people, in particular most people participating on this thread. Of course you can obtain Halcyonics or TLC or other expensive devices, even the Vibraplane and Minus K are not exactly inexpensive, but if you have many components to isolate one trusts you have really deep pockets for all active devices. Obviously for speakers the problem is a little, well, quite a bit different since the speakers only go down to what, 35Hz - if you’re lucky. 

Yes expensive. But buying used you can get them for the price of a minus-k and they come up regularly from instrument sellers on eBay

 I'd argue that anyone with a $10k plus vinyl rig should definitely invest and some would suggest that a $5k turntable on such a platform can outperform a $20k one without it and my experience says that could well be true

Thank you Geof again for explaining this hole isolation problem every audiophile is having to deal with,
I am happy with the spring type speaker isolation platform but i am considering placing a ball bearing type platform on top,
The product is a three piece wood type materiel sandwich,
I would place the bottom slice on top of the podium roughly the same size as podium platform , Then you place the middle slice with cones at the bottom and discs cut out with balls in on top , so when you add the top layer the balls and cut out discs line up creating circular bearing movement,
With the podiums using there spring type system i believe this could add further isolation so increasing again sound quality, the bearing product is a cheaper type Symposium type platform.
I am finding the mpingo discs extremely effective, i am going to order some of your crystals that rest on the rca connectors where i cannot put mpingo discs 
Thanks for every piece of information you have posted on my discussion,
Am i correct in thinking the mpingo discs are dealing with airborne and internal equipment born vibrations,
My aim is to reduce all vibrations that are in my system done to next to zero if possible,
This isolation journey started for me years ago with the SR migs , then found i worked my way up to stillpoints which if i can remember so much has been and gone i got great results but the prices were high and have just gone up again,
If money was not a problem i believe Seismic Podiums with stillpoints would be a very effective isolation pairing,
With the odd mpingo disc here and there, maybe i should remain happy with the springs and get a loan for the stillpoints sounds like a joke but also could be the ideal solution any opinions or ideas anyone on the springs with stillpoints?