I have had an Apple Airport Extreme for many years and it finally did not power up one day so I quickly narrowed in on an Asus RT-AC68U and it works for the two Macs and several windows machines in our house. Since it has 801.11AC.
I wanted to bring my older Apple machines up to that speed and went on the market for a good USB adapter that would work with OSX Yosemite. I have never had a problem buying an -N adapter and using it interchangeably between windows and OSX but -AC adapters seem to be different in this.
I tried a Netgear A6200 and learned there were no drivers for OSX. I looked at several other "name" brands and they either had no OSX drivers at all or the last working driver was for 10.8 and Yosemite is 10.10.
I finally stumbled on this adapter and after downloading the 10.10 driver from thee Netis web site it connected and works great. I have done limited testing so far but the results are promising. I have a late 2012 Mac Mini that is two floors and 50 horizontal feet from the Asus router.
Comparing the Netis adapter to the Mini's internal wireless i saw a 40% improvement in transferring a file from my Mini to a linux server that has an ethernet connection to the router. On reading files the transfer improvement was 100-140%. When testing internet access there was no difference because Comcast is the bottleneck.
The software is fairly barebones but it was easy to look through the list of available networks, click on mine and then enter the password. I have seen 85-90% signal strength and given the about of wood and drywall between the router and my office I am happy with that.
The USB extender cable & cradle has a cable length of over 5' 6" which made it possible for me to position the antennas where they got good reception and did not clutter my desk. The size of the adapter with the antennas up could be an issue if I was carrying this with my laptop.
+ Works with Mac OSX Yosemite!
+ Measurable speed improvement over -N connections
+ have not experienced any dropped signals
+ Website is easy to navigate for 10.10 driver (10.8 was the latest on the included CD)
+ A USB extender with a stand is included in the box (not all of the competition include this)
- The adapter, antennas and stand is too large to be easily portable
- It does not use the standard Apple WIFI software (which is an Apple issue and not Netis')
Bottom line - While I had never heard of Netis before this I am glad that they have accomplished something that their larger rivals have not - getting an 801.11AC adapter to work under Yosemite (OSX 10.10).