@Hedda , I think you write some helpful and knowledgable posts about Zigbee, however I think a statement such as :
“Zigbee … its limitations (e.i. extremely sensitive to interference, poor reception)”
is quite the opposite.
To blanket say that a device in the Zigbee universe is any more susceptible to “interference” and have bad “reception” is not a true statement.
A discussion on this could go on for many 
s.
I will just ask, how can a device that can be built on the same piece of hardware that runs, Zigbee, Bluetooth, WiFi or other 2.4 Ghz 802 protocol just with a change in firmware be as you say “sensitive to interference, poor reception” with one firmware vs. another. All are using the same physical and lower level firmware for their same radios?
Sure argue that different approaches to power profiles of a device, especially a battery powered one can effect a universe, however again you can make any of the firmwares I point to suck, if you are not well versed in the design. But that is very different than saying Zigbee is going to be worse than one of the others just because it is Zigbee.