I have them. Bought to be honest. And EH. But I can live with this 1% difference, because casters still seem to be carrying and casting haste. I don't think its the rarest, it just is the one which lack you notice most.I will say the most useful variant, fort115, seems nearly nonexistent.
After aquiring this boots, I must admit, I didn't yet bothered with visiting fred to swap BS for other feat. And in fact, I have problem with chain of gearswap, mostly because vitality augment is not dropping for me.