The USB ports can be used for a lot of functions. You can connect USB external storage devices or printers to these ports and turn the router into a storage or print server, both of which I found worked well and were easy to set up. With the RT-AC66U, these ports can also be used to host storage over the Internet via a feature called AiDisk, coupled with a cellular USB dongle so the router can work as a mobile hot spot, and when an external hard drive is connected you can also use the router to manage downloads by itself.
The router's PC-less download feature, which didn't work with the router's initial firmware versions, now works as intended in my testing. It supports all type of download services, from regular HTTP downloads to newsgroups to Bit Torrent. The feature can be easily managed via the Web interface and can handle multiple downloads at a time. Unfortunately, in my trials, it couldn't download from sites that require authentication, such as RapidShare. This support might be added via a new version of the download feature or a future firmware update, however.
The router's AiCloud feature, which was also not available before, has, with the latest firmware, become a major feature of the router. AiCloud allows users access to not only sharing/streaming content stored on the connected external drive to iOS and Android mobile devices (or computer via a browser), but also content on the computer connected to the router. This means you can easily share data stored on any computer in the network to remote users. For this feature to work, you need to know how to set up a DynDNS account, which can be done in a few steps within the router's Web interface. I tried this feature out and it proved to be a very handy feature for those with fast Internet connections.
Lastly, the Advanced Settings offer more in-depth access to the router's features, some that would be specifically useful for businesses. The most notable feature is the VPN server for creating a secure virtual private network for remote users. You do need to possess decent networking know-how to set up and manage a VPN. The router also supports IPv6, a customizable firewall, and QoS.
Overall, like the RT-N66U, the RT-AC66U offers many useful features you might want from a high-end router and generally the work very well. Asus says it will continue to update the router's firmware to offer more features and improve the existing ones.
As a 5GHz router the RT-AC66U offered stellar performance, with the fastest data rate I've seen yet. On the 2.4Ghz band, the router wasn't the fastest but still performed decently.
I tested the router with both 802.11ac clients and regular Wireless-N clients. Since there are currently no devices on the market that support 802.11ac, I actually used a second RT-AC66U unit as a media bridge for the 802.11ac Wi-Fi test. At a distance of 15 feet, the Asus registered the fastest Wi-Fi speed I've seen, scoring 339Mbps (or about 42MBps, close to the speed of a Gigabit Ethernet wired connection). At this same distance, when used with a Wireless-N client, the score was also impressive at 208Mbps. When I increased the distance to 100 feet, the router's speed was lowered to 179Mbps and 167Mbps for 802.11ac clients and Wireless-N clients, respectively, still very impressive.
On the 2.4GHz band, where the router works with only Wireless-N clients, it scored only 66Mbps and 50Mbps for the close-range and long-range tests, respectively. These placed the router in the top four in terms of 2.4Ghz data rates. Note that the router was tested at CNET Headquarters in San Francisco, where there are many other Wi-Fi devices, especially on the 2.4GHz band, that might interfere with the router's performance.
In that same environment, the RT-AC66U offered very long range, up to up to 300 feet in my testing. It was also very stable and passed my 48-hour stress test with no problems. During the stress test, the router was set to continuously copy data back and forth between multiple clients, both wireless and wired. Neither of its wireless bands disconnected during this time.
The router offers decent network storage performance, when coupled with an external hard drive, with 134Mbps for writing and 77Mbps for reading over a Gigabit Ethernet connection. These speeds are fast enough for light media streaming and data sharing.
I noted that with the latest firmware, version 18.104.22.168.246, the router seemed to be hotter than before during heavy loads. While it wasn't hot enough to be alarming, it should be used in an open space.
(Longer bars indicate better performance)
(Longer bars indicate better performance)
Service and support
Asus backs the RT-AC66U with a two-year warranty. At the company's Web site, you'll find downloads, FAQs, a manual, and other support materials. If you want to contact the company's tech support, however, it's better to do that via e-mail as there's no tech-support phone number listed on the Web site.
With great performance and lots of useful features, the Asus RT-AC66U, with the latest firmware, is one of the best 802.11ac-ready routers on the market, worthy of its hefty price tag.