I have been using the Actiontec MyWirelessTV 2 to share a cable box between my guest room and my son's room. They are about 15-20 feet apart, down a hallway. It's not perfect but it does work well.
Occasionally I have to reset it but it's hard to say if it's the Actiontec or the Xfinity X1 box which it the culprit.
As far as picture quality, it looks identical to the cabled connection. I got it from Jet.com with their initial 15% off discount so it was just over $150.