Weaknesses: Obviously I would like them to be cheaper. My main problem with them is that if they are tumble dried the innner sock contracts too far and it's then hard to get them to fit your feet well.
Overall: I love these socks. I blister at the merest sight of shoes, but these have made longer distance running bearable. I still get the odd blisters, especially when upping my mileage before a marathon etc, but without my twin skins I doubt I'd manage a half-marathon, let alone a full.