The State of iBeacons (June 2015)
This is pretty consistent with my experiences. On observation I’d add about squirrely RSSI values – readings walk around a bit. You’ll do better to calculate a moving average and toss out the occasional 0 reading. Also be mindful of your iBeacon’s power settings – you may need to calculate your own distance from the RSSI value if the device isn’t transmitting at the default power expected by iOS. Even so, distance may not be entirely accurate. Take it with a grain of salt.