here to share my test with the AP50 with double mode (2,4 and 5Ghz)
location: I have an office 140 square meters at the first floor in the center of a town in North Italy
I have used as wifi device an IPhone 4.
I walked downstairs keeping a conversation on skype and it worked walking around up 25 meters.
I have been able to refresh web pages up to 70 meters from the access point
The access point is located next to a window but inside the flat.
I hope that it helps.