This is an excellent Dual Band router.
First let me clear up any confusion and confirm that it is fully compatible with any broadband connection: ADSL, Fibre, Cable...
That said, it is a wireless router only, therefore with which ever broadband connection you have, you will always need a modem. The (main) internet connection input uses a gigabit ethernet port, so you would need a modem which connects via ethernet AS WELL as this unit. Here are my recommendations to do this;
ADSL / ADSL2+ (TalkTalk, Sky, Plusnet, BT, EE, Primus, etc) :
TP-Link TD-8616 Modem: http://amzn.to/1msigtF
DrayTek Vigor 120 Modem: http://amzn.to/1jM5lIk
Any ISP supplied modem/router by ideally using a modem only mode if available or turning off any routing/wireless/firewall functions and connecting one of the LAN ports to the WAN port on the RT-N66U.
Fibre 38 Mbps / 80 Mbps (FTTC, TalkTalk Fibre, Sky Fibre, Plusnet Fibre, BT Infinity, EE Fibre, Primus Fibre, etc) :
Ask BT Openreach to leave you a standard VDSL modem when they come to activate your line, or again, you can use any ISP supplied modem/router by ideally using a modem only mode if available or turning off any routing/wireless/firewall functions and connecting one of the LAN ports to the WAN port on the RT-N66U.
Cable (Virgin Media) :
Switch the "Super Hub" to modem only mode, and connect the LAN port to the WAN port of the RT-N66U.
Once connected to your modem, set up and connection works flawlessly. Asus seem to get bad press for updating their firmware for some reason? I see this a good thing as their development team are working to improve their products, unlike Netgear which release a product and never intend listening to customers and improving on it. The first thing you should do is check for updated firmware. Type (usually) 192.168.1.1 in your web browser, log in, click Administration -> Firmware Upgrade tab -> Check. Upgrade if necessary. More details can be found on the website here: http://www.asus.com/Networking/RTN66U/HelpDesk_Download/
To make the very best use out of this router, you would want a wireless N dual band compatible device, and connect on the 5 GHz frequency.
Its simple to upgrade most laptops (HP's are an exception!) providing you get the correct size adaptor:
Intel Dual Band Wireless-AC 7260 Laptop Network Card (Full Height) : http://amzn.to/1pcdvMy
Intel Dual Band Wireless-AC 7260 Laptop Network Card (Half Height) : http://amzn.to/1q3pU1c
As with all wireless networks, walls are the biggest problem, especially if you have thick walls or 3 floors. In that situation, you could physically move the location of the router to another location, and run a network cable to the modem, or use a wireless range extender.
Without going into too many tweaking details (as it is usually site specific), generally to get the best performance, any wired devices should connect using gigabit ethernet with Cat6 cable, and the wireless channels should be set to use 40Mhz bandwidth on a high channel number (2.4 GHz) if your devices support it, and 40 MHz bandwidth (5 GHz channel), again only if your devices support it.
It has many advanced features; in built VPN server (connect to your home network while connected to someone else's internet), USB 2.0 file / printer sharing, mobile 3G or 4G tethering, parental controls, traffic manager (QoS), isolated guest network, AiCloud (virtual drive), custom firewall, IPv6 compatibility, It is also supported by DD-WRT if you need professional functions.
I have 2, to create a network bridge - ie one is downstairs in the house connected to the modem - primarily for wireless devices to connect to the internet, then the other unit is outside in another building and connects 4 wired devices to the network. The link speed is 300 Mbps, and has been active for over a year without any problems.
If you have the extra to spend, you should consider the latest Asus router, which uses the newer wireless AC standard;
Asus RT-AC68U Wireless Broadband Router : http://amzn.to/Uifvod
Overall this is a brilliant router that out performs any other brand in its class and it is still been actively supported by Asus.