I find the absolute strap on my Aeronaut to be a bit uncomfortable after a while but in backpack mode it's great. I think the weight is too much for my shoulders no matter the strap. Plus with the extra weight you get more "swing" going which I don't like. Only problem is I normally have a backup as my second carry on bag and that has to be hand held, which works but isn't optimal.
I find the Aeronaut in backpack mode to be very comfortable.