I have had lots of On trainers and these are exceptionally comfy, but the first thing I always do it replace the laces with elastic "Lock Laces" as I find this improves comfort makes putting them on slightly less of a pain (Plus no laces coming undone). However, with the CloudAce, I found that I developed a blister on the bones of each big toe where the lowest lace whole is. This is because of the "Lock Laces" being thicker than the laces it comes with and it formed a small bump underneath the hole which presses into that foot bone. This got worse over the next 3 or 4 runs and I was forced to return to the stock laces where this problem does not occur. I have not had this with any of the CloudFlow or CloudFlyer trainers in the past. This is not a deal breaker, but I would appreciate it being taken into account in the next edition.