I went from an Ultimate Direction AJ to this, and then added the Double Barrel to my collection. I use either this or my Double Barrel depending on length of run. The UD AJ is good if I need to carry more stuff with me, but for this most part in my runs, and definitely in my races, this will be the way to go. I Get a little lateral (lats) chaffing, but nothing horrible. Yesterday, over 6.5 hours and no visible chaffed areas the next day. I was slightly rubbed post run, but not bad. I typically snug things right down to get a no bounce fit, and make sure the bottles ride high, which makes it a little more comfortable. It truly is by far the best system I have used to date, and in major heat, the only way to fly - not much to add contact to your body and increase body heat.
My only other illegitimate complaint would be that cell phone access is only had by taking the Hydraquiver off and unzipping the back to pull the phone out. I will say though - this is super easy to do, and I have yet to lose a bottle while swinging it off to grab my cell phone (camera)..
As stated above, after running in the single, I added the double to my repertoir. I am pretty damned impressed with both. My chaffing can also be body (build) dependent. I’m 6’2” and 185, might fit better or worse on someone more slender or less slender.