The RT-N13U's design most closely mirrors the design of many of Netgear's routers, albeit in a smaller form factor. It's a vertically mounted router with a moulded plastic base. The practical upshot of that is that it only visually works vertically. If you placed it on its side it would have a rather unfortunate tilt, and there's nothing you can do to change it. The back of the router houses four standard 10/100 Ethernet ports, one inbound Ethernet port and a single USB 2.0 port.
One interesting part of the RT-N13U's design is that one of the key functions of the router isn't controlled by software, but by a switch on the bottom of the unit. Normally hidden from view, this lets you choose between router, repeater and access point duties for the unit, depending on your needs.
The RT-N13U is an 802.11n router working solely in the 2.4GHz band. They're becoming increasingly common, even in the unit's admittedly attractive price range. The other feature that Asus heavily promotes with the RT-N13U is its ability to work as a print server via direct USB connection. The RT-N13U also offers a BitTorrent client utility, called "Download Master". Once installed, it'll shift downloading duty to the router, with right-click functionality in supported browsers and the ability to download directly through the router rather than the PC whenever you like. To get that particular function to work you'll need to insert a USB Flash drive in order to have somewhere to store your downloaded torrents and files.
The single USB port on the RT-N13U has a double duty to perform. Plug a USB drive into it, and the RT-N13U acts as an FTP file server to any connected client. Plug in a USB printer and run the Windows-only printer sharing client, and you can share a printer to other connected clients, even when the original set-up PC is powered down. The only real shame here is that the one port has to perform two functions, meaning you've got to pick between them.
Configuration of the RT-N13U can either be performed with the supplied installation CD or via a fairly standard web interface, which splits the unit's functionality between a simplified interface, complete with its own animated guide. Asus' guide is called "Dr Surf", and frankly we found him pretty cheesy and not all that useful if you weren't already au fait with networking terminology anyway.