I first learned of the GAIA from VPI's Harry Weisfeld, who found them to provide a noticeable improvement to the sound of his KEF Blade loudspeakers. Some VPI turntable owners have posted on the VPI Forum their positive findings of the improvements the GAIA made in the sound of their VPI tables. About a year ago I made a posting there asking if anyone had compared the GAIA with the Townshend Seismic products (the individual Pods, and the Platforms, which include Pods), and received no responses.
Not wanting to shell out for both GAIA and Townshend feet, I carefully analyzed the design of both. There is a detailed diagram of the internal structure of the GAIA on IsoAcoustic's website, and it appeared to me that the metal structure of the GAIA is not the aspect of the foot that is providing whatever isolation it affords. Deep inside the GAIA is a layer of some rubber-ish material, presumably of a proprietary nature (though not necessarily: it could be Sorbothane, Navcom, or EAR IsoDamp). It is that material which appears to be the main provider of the GAIA's isolation properties. The GAIA is priced in accordance with each model's weight capacity: $199/ea for the GAIA III, $299/ea for the II, and a whopping $599/ea for the I.
In contrast, the Townshend Pods are the same price for all models, and the weight divisions are much more finely-graded than the three GAIA models. More importantly, the design of the Townshend is completely different. I won't go into that design here, as the Townshend videos on You Tube explain it (and demonstrate it) very well. I suggest watching the videos, and seeing what you think. The Townshend Seismic products have received little press in the US (look out, Dylan ;-) ---aside from Robert Levi in Positive Feedback) ---but quite a bit in the UK. Links to reviews are provided on the Townshend Audio website. US dealers of Townshend Audio are few and far between, so getting a set for audition is unlikely.