I'm on my fourth pair of Runomocs. I had two pair of the originals, with the 5mm sole and now on my second Dash with the 2mm sole. I have yet to go backpacking with them, as I tried that with the Merrill Barefoot, on a rocky trail and my feet didn't feel too well, afterward.
I do like the fit and true flat walking surface of the Softstars better than the slight toe rise of the Merrills though. It seems to me that the 2mm sole lasts longer than the 5mm one, at least on pavement and the leather part is still going strong, after many miles, so I don't think that is so much of a concern.
I've been trying to toughen my feet up for a backpacking trip, in them, for the past year or so, wearing them most everyday, but I don't know if it's yet enough to counter the years of wearing padded and heeled shoes. I think people that go barefoot outdoors a lot, stand a better chance of using these shoes for backpacking. If it's just hiking without weight, then I think they are great, but keep in mind that they are not designed for walking with a heel strike, rather a mid foot strike. It's easy to bruise your heel, with no padding there, so it takes some time to learn how to walk again, as if you were barefoot. :)