This is a well designed and implemented bag. Several waterproof bags follow the same concept - you roll the open end down several times and it prevents water from getting inside. This bag follows that same design so nothing special there, however the material is thick, sturdy, and wear-resistant. The different color choices are great; we've ordered a couple of them and the different colors help us identify at a glance what's inside when they're all piled together.
I should say if you order the larger sizes it can be a pain digging down to the bottom to find something, first in last out, but you know that going in.
The waterproof phone case was a bonus. I didn't really order the bag to get the phone case, but my wife snatched it up and was delighted with the case. It's a bit harder than normal to control the screen but it is touch sensitive and you really can use it while inside the case.