Man oh man! I have been wearing FiveFingers for years now; again and again purchasing the TrekSport model but when I was notified that they were on limited release and would most likely be taken out of Vibrams rotation, I thought I was downgrading when I purchased these due to the thin sole (thinking they would wear out in a matter of months) - I couldn't be more wrong. Let me first say I the TrekSports have EVERYTHING going for them. It has been Vibrams ultimate design, or at least I thought for me that no other FiveFinger would come close to the versatility of the TrekSport. So when I went to order the TrekSport again they were completely sold out and I was told they would not be re-stocked. I was crest-fallen. So I purchased the KSO's and OH MY GOD....I can't believe that I would love the feel of another pair of Vibrams as much as the TrekSports but now that I have a pair of the KSO's AND the TrekSports, I've noticed myself wearing these EVERYDAY, ALL DAY. So what does this all mean? I've SO found the top dog in the FiveFingers line-up! Possibly never needing to go back to the TrekSports.......MAYBE!