I've been using Isoacoustics for my Wharfedale 220's and am quite happy with them. Bought them primarily because of space constraints. Had tried foam etc, but overall I would say they are an improvement over using books, foam, ply etc. Member Tuff has a pair too and is one of the reasons I bought them.
What do they do ? They will raise your speakers to two adjustable heights with a minor tilt adjustment. Primary benefit as per my understanding is decoupling. My personal experience is that they did help clear up mids and tighten bass.They also allowed me to place speakers as per my whims. But please note that speaker placement, accessories while important usually bring only small improvements in sound. Best solution is better speakers.
On a side note, on the Wharfes the bass port fires down into a plinth which results in dispersion on all sides. So the port is already pretty close to whatever surface you place it on, unlike most speakers which have bass ports higher at around mid-level. Don't know if that's the reason for my perceived improvement. Also I removed the plinth(easy screw removal) and which converts into a true down firing port. But could'nt hear a difference.
Bottom line. If you have enough space, dedicated speaker stands might be a better choice. Especially since price differential might not be much. But if you have space constraints or have made your mind up then these should make an audible difference. You can check out the amazon us review too.
Hope this helps.