Comparing this to a similar bag I have from Eddie Bauer. Wanted this one because it holds two small water bottles (my other bag holds one) and I like the phone pocket. Problem: The piece of plastic ware for holding the strip in place is harder to use than my old bag. Another problem: Though there are two water holders, (my old bag has one), and they are very small and hard to use. Plus, for 2-3 hour hikes I only want to carry one small water bottle. So I'm not sure I actually care about the double water holder.
Since I usually carry my phone in my pants pocket anyway, today I used my old bag for hiking since it's easier to use plus it's lighter and it's very hot out. I was perfectly content using my old bag. Once it gets cooler I may use the Waterfly bag again. We'll see.