I have used Fly Rope for about 4 months.
I am relatively new to climbing, 3rd season. I mostly climb on Braided Safety Blue by New England Rope. I have also climbed on Blue Streak and 7/16"Sport Line. BTW, Fly is true 11 mm diameter.
My comments about Fly are: Rope is very supple even on first use. I also found it to grip extremely well. My experience with new rope is that it is waxy and a bit creepy on first use. Not so with Fly.
It is also very compact. I have pretty small hands, so the blake's hitch is 1/2 of a handful rather than a whole handful with 1/2" rope.
It also stays round. My experience with Sport Line or other non-cored rope is that it deforms as it is loaded in the blake's hitch. Fly acts just like cored arborist rope.
Bottom line, I like it. I am going to keep using it. I'll probably buy more. I can't find any downside to it.
Bob
Tree Climbing for ALL
www.arborquest.org