I concur with Frank.
Initially, they seem like a middle ground between stocks and TG's. The tension and stability of ThunderGuts. IMO so far, they seem to have 80-90% of the ThunderGut sound, but the feel is a little more slippery, which I like. Still not as slick as the stocks but less tacky rubberness. That was one of the deal breakers for me on the ThunderGuts. I have been so busy that parts of my rig are in my trunk so I will have to wait til tomorrow or Saturday to give it a proper amplified test.
About stability: I strung it up and played about an hour, bringing them up to pitch every few minutes. About 2 hours later I tuned it up again (it was about 20-30 cents flat across all strings). 12 hours later the G string was 20 cents flat and the other 3 were almost at pitch. We are talking hours vs. months on stabilizing.
One initial thing I noticed that is similar IME to the TG's: especially on the thicker strings, there is a harmonic (4th fret harmonic) that is very prevalent on most notes on those strings, and it sounds a little out of tune. At first I thought it was because the strings are too thick to fit all the way down in the nut (except for the A) but is is pretty consistent on fingered notes up and down the neck. The G string is the purest harmonically and it is the most out of the nut slot.
For you upright players, they have a subdued sustain and growl like spirocores. I hope they settle in and darken over time. ThunderGut users: do those mellow over time at all, or do they keep their tone indefinitely?
After less than one day, I am thinking these are worth living on the Hog for an extended period of time. Their dark charcoal color is the whip, too. I will continually report back. Saturday I have a gig on it and can put it through the paces live. I hear these will be available but don't know exactly when.