I've always wanted to try velocity until I got my hands on it in a store and felt the 'sure grip' coating. That tacky feel might be good for gripping your hands, but might it lend its gripping quality to the tree branch/crotch? I supose it can't be too bad or they wouldn't make it like that.
I've climbed on 1/2inch 12 strand nylon, which feels awesome but the nylon wears quickly, glazes and once fuzzy, the fall line acts like velcro to shaggy bark. Arbormaster has served me well for two seasons though I find it to have too much elongation/bounce. My new favourite line is Petzel 'Vector' 11mm; it's a static line (no elongation), is rock solid/round, a little stiff which helps prussik performance and is light weight. (just be very carefull due to its lack of shock absorption).