Advantages over Airport Express + Airfoil
Airport Express and Airfoil are 2 of my favorite products, but no good for watching movies - way too much delay. The Audioengine wireless is about the same price as AE+AF, but there's no setup headaches and AW1 has a latency of under 20mS so it's fine for movies (no lip sync problems).
I have one AW1 pair going from my surround receiver out to my AS8 subwoofer and another pair going to powered rear left/right rear speakers (A5's of course).
As far as range goes, I get about 50-60 feet around my house through 1 floor and 2 walls. I also have 2 wireless networks running and no co-existence issues so far.