Looks like my bundling up of the ASUS RT-AC66U was a bit premature. I received my Airport Extreme yesterday. After a quick phone call to Verizon to 'break my lease', configuration and setup went relatively fast. My wired connection was super fast, as expected. Devices seemed speedy and my Airport Express was still in place, its job is to extend my wireless network to the furthest point in my home. Typically, this bedroom is the worst for WiFi connectivity. Routers alone don't help, but since installing the Airport Express, it hasn't been a problem.
My reason for going back to an Airport (the Extreme would be an upgrade from my previous model) was for increased stability. I was thinking that perhaps my Nest wouldn't go offline as much and my TiVos wouldn't drop connection between each other. These don't happen often, but I had hopes it would improve to where it never happens.
Continuing my testing, I fired up my Dropcam which is setup in this far bedroom. It's a good test device, since it demands a good connection. Within a few minutes, it started dropping the connection and the error message indicated a slower than necessary bandwidth. This was never an issue with the Asus. Using my iPhone 6, I opened Speedtest and did two checks while sitting in the room. I then installed the Asus and asked Verizon to once again break my lease and reboot my ONT. That's the process for switching out routers. I went back to this bedroom and fired up Speedtest. The results were overwhelmingly in favor of the Asus.
I boxed up the Airport Extreme and at some point, I'll upgrade to the Asus RT-AC68P (or U). The P is exclusive to Best Buy and has a slightly faster processor. Helpful if you are connecting a USB drive. This might be a good option to setup a TimeMachine for my wife's computer.
The Netgear R7000 Nighthawk is still a consideration, but I'm not a fan of their admin interface. People seem to suggest they don't support their products once a newer model arrives. ASUS routers have good support and allow for open source firmware. People seem to rave about Merlin's firmware releases. Since I'm back on the RT-AC66U, I updated to Merlin's latest release. Maybe that'll provide the improved stability I was looking for from the Extreme.
Moral of the story...the grass isn't always greener, even if it comes from Cupertino.