I bought one of these here on Audiogon to use with my little modded Rogue Tempest II and am very happy with it. It replaced a modest after-market cord, and the resulting changes were instantaneous and remarkable. Although I did not experience (as some above did) an expansion of the stage, I did experience less "jitter" sound in the mid treble (I run CD only, and power cords - even amp cords - can affect this for some reason), less bass overhang and smearing (i.e., "tighter" bass), more solid imaging, and a generally clearer, less veiled presentation from all of my CDs. I did not hear any obvious warmth or coolness - sounds pretty neutral to me, although I've heard others comment differently (i.e., that it is a warm cord). I've been at this for 30+ years, and I expect a good power cord to do these things. I have owned Electraglide, Cardas Golden Reference, Synergistic, and others, and this is easily the best of the bunch I've tried. It has an excellent "palp factor" and lets the music ebb and flow properly with wonderful microdynamics. It isn't miraculous, mind you. It's just that it does all of this better than other power cords I've owned. It is an 'end of the road' cord for me.
This brings me to the pricing of these things. I have spoken with Mike about this (he is a really nice guy, if emails count for such things), and we see price structuring differently. I don't know who actually buys these things for thousands of dollars as they are listed, but the real price (as best as I can figure) is far less than that. My point is that if people realized they could actually buy these things for their "real" price, more would be sold. I will now step off my soap box.
That quibble aside, I have to say that I am thoroughly pleased with this purchase, and impressed with the quality of this cord. I have sent amps out to be modded for more than this, with less of a benefit than just sticking this cord in the business end of my Rogue. My guess (but it is only that) is that it would make an even larger difference on more sensitive and detailed equipment than I will ever own.
In any event, I thought I'd add my "me too" to this string. The GI brings the illusion of real music in my room one large step closer, and about as large a step as any power cord in my experience can take. If you are considering a more "main stream" cord from the companies listed in this thread, you would do well to put the GI on your short list. It is the real deal.