The web interface also has too many preconfigured settings for games, and it's laden with gamer-specific lingo. If you want to program the router for something unrelated to gaming, you'll have hard time finding the right section to start with. For example, the built-in protection function of the router, which is normally aptly called AiProtection, is called Game IPS on the GT-AC5300's interface. Similarly, the QoS feature is called Game Boost, and so on.
The interface isn't the worst thing in the world, and you can probably get used to it after a while. Still, the router would be much more user-friendly if it had an option to change the theme to match that of other Asus routers.
With the GT-AC5300, Asus has also introduced a mobile app, called Asus Router, that's much easier to use and allows users to do most of what they can with the interface. However, this mobile app only works locally, when your phone is connected the router's Wi-Fi network.
The GT-AC5300 did well in my testing, registering a top sustained Wi-Fi speed of almost 750Mps on the 5GHz band. Its 2.4GHz performance wasn't as impressive, however, coming in at about 90Mbps. This is a normal for most recent high-end routers, where the 2.4GHz frequency is there only for compatibility. The router also delivered a Wi-Fi signal over a very long range. I was able to get a sustained speed of more than 100Mbps from 150 feet away.
The router passed my 48-hour stress test, during which I set it to transfer a large amount of data between multiple clients, and it didn't disconnect once.
I tried out most of the the gaming features with a few games including Diablo 3 and Start Craft 2, which worked as intended. It was impossible for me to test them all since the list of supported games is quite long.
Should you get it?
If you play games often and you can afford it, the GT-AC5300 is the best router you can get. Just be prepared to handle its interface. On the other hand, if gaming is low on your priority list, many other routers, especially the Asus RT-5300, and better yet, the RT-AC88U, will give you a very similar experience at a lower cost.