It's like four networking products in one! — I installed an AirPort Express near my TV (and game consoles), then had my existing AirPort Base Station automatically configure it as an extender.
- Wi-Fi base station: This is what they most advertise. Plug in your existing local network or your Cable/DSL modem directly, and then configure it to share the internet around your home or office!
- Wi-Fi extender: Use it to extend your current AirPort wireless network, or to bring wired internet to places not wired. It works in the reverse of the method mentioned above, and requires an existing AirPort Base Station of some kind. (But, it could even be another AirPort Express!)
- Wireless/wired print server: Plug in your printer via the USB port, and have it shared to all compatible machines on the network! (Even Windows machines with the “Zero Config Wireless” service enabled will be able to see it.) 🖨
- Wireless audio link: There's a 3.5mm audio output (with optical support) for streaming from iTunes and some other apps on your Mac. 🔊
… My AirPorts talk securely over the air, while the new AirPort Express provides a media link from my Mac Pro and MacBook to my stereo, and an Ethernet port for my Xbox to get onto the Wi-Fi.
… I was skeptical at first that the functionality would be limited given the name of the product, but it's definitely great… even standalone without a normal AirPort on the same network! 👍🏻