I have a z-wave device in the garage for the garage door, and it's about 30 feet and 2 walls away. I also have a z-wave outlet on the back deck with 1 wall and about the same distance. Both have worked flawlessly.
Now the zigbee door/window sensor in the garage on the garage door doesn't seem to always report the correct status, but it's another 8 feet away, so I'm not surprised. Hoping to switch it over to z-wave, and also add something else in between to solidify the connection for both of the garage devices. That and I'm a geek and want everything z-wave now, so that's my excuse.