Just set one up at my InLaws... Replaced an Apple Airport Extreme and 3 Airport Expresses... fastest Wifi I have ever used!

They have about 4500sqft

I picked one up too, no complaints. Have a three story townhouse so I was having suboptimal Internet at the top. Much better now. Easy to set up and get going.

I set one up Friday. I was having connectivity issues with my Fire TV Stick that are apparently related to old, single band routers.

Set up was easy, I'm the only guy nearby with 5 GHz band, and the Fire TV Stick works great. I also like that it has a physical on/off button for those times you have to restart everything.

FWIW, I actually got better coverage and speed throughout that coverage with the Nighthawk X8 in a 2-story 2800 sqft house (even covers the entire garage and backyard incredibly well). It does have the advantage of being somewhat centrally located though, so not quite the Orbi target audience.

You can't go wrong with any of the new mesh units. I went with the Amplifi HD because I have been a Ubiquiti fan. I haven't had one complaint, and love the app and look.

One of the first Mesh WiFi reviews: http://www.smallnetbuilder.com/wireless/wireless-reviews/33020-mesh-wi-fi-mashup

How does this compare to the Google WiFi? I am debating between the 2 but I do like that the Google system has 3 units for a cheaper price. I just don't want lower quality.