Taken from : http://www.macnn.com/reviews/apple-airport-express.html
Apple Airport Express
March 18th, 2008Wireless audio streaming, USB port sharing, and WiFi
Appleís new Airport Express is a multi-purpose device that can perform a variety of functions. First, it can create a wireless network for up to ten computers to share a single cable or DSL modem. Unlike the previous version of Airport Express, the new version now supports the 802.11n draft standard in addition to the older 802.11a/b/g standards. By using the 802.11n standard, Airport Express not only makes your WiFi connections faster, but allows you to maintain a WiFi connection from a longer distance away from the Airport Express unit.
Secondly, this WiFi connection also allows Airport Express to share a single USB 2.0 port so multiple computers can share a USB printer. This essentially lets you use the Airport Express as a wireless USB connection so you can place your computer in one room but put your printer on the other side of the room or in an entirely different room altogether.
A third function of Airport Express is to use its wireless capabilities for streaming music from iTunes to the audio port in Airport Express. This lets you plug speakers into Airport Express and listen to your iTunes music collection in another part of the house.
Basically, you can think of Airport Express as a wireless extension cord for replacing an Ethernet cable, a USB cable, and an audio speaker cable.
Airport Express provides wireless Internet, USB port sharing, and iTunes audio streaming
The bottom of the unit provides a 10/100 Ethernet port, a USB 2.0 port, and an audio jack
Setting up Airport Express is simple. Just plug the unit in and run the Airport Utility program that comes on the included CD, which runs on both Mac OS X and Windows XP/Vista.
After Airport Utility scans and recognizes Airport Express on your network, youíll have a choice of adding Airport Express to your network or replacing an existing device with Airport Express.
To protect your WiFi network, Airport Express allows a choice of WEP or WPA encryption. Although WEP encryption is better than no encryption at all, WEP can be easily cracked so most users should choose WPA encryption instead.
You can replace an existing WiFi device with Airport Express
Airpot Express allows encryption to protect your WiFi network
WiFi Internet Sharing
If you donít have a WiFi network, you can plug an Ethernet cable from your cable or DSL modem and create a WiFi network simply and inexpensively. If you already have a WiFi network, you can use the Airport Express to extend your WiFi networkís range.
Plug an Ethernet cable from your cable/DSL modem, or router, and plug the other end of the Ethernet cable into the Airport Express. Unlike the Airport Extreme base station, which uses the faster 10/100/1000 Ethernet port and provides three additional Ethernet ports, the Airport Express only offers a single 10/100 Ethernet port. This means you can only plug an Ethernet cable into Airport Express to create a WiFi network and you canít take advantage of the faster 1000 Gigabit Ethernet speeds.
If you need the fastest Ethernet speeds or need an Ethernet router, Airport Express is not for you. However, if you just need to create a simple WiFi network, Airport Express is small enough to toss in your pocket and take with you anywhere you can plug it into an electric outlet.
If you just need to create or extend a WiFi network, you can find less expensive options. What makes Airport Express unique is its ability to wirelessly stream audio from your iTunes collection. Basically another computer running iTunes streams the music to Airport Express, which plays the music through its built-in audio port where you can plug in speakers.
Unfortunately, you need to buy separate audio cables to connect your speakers to Airport Express, or you can opt for Appleís own $39 Airport Express Connection Kit, which includes a Monster mini-to-RCA left/right audio cable, a Monster mini-to-optical digital Toslink audio cable and an AirPort Express power extension cord. Without the power extension cord, youíll be forced to plug the Airport Express unit directly into an electrical outlet. The lack of any included audio cables means you canít use Airport Express to stream audio right out of the box without an additional expense.
Airport Express can act like wireless audio cables connecting your iTunes computer to speakers
Another potential problem is that Airport Express can only stream audio from iTunes. If you donít use iTunes or need to stream audio from a different program, you canít without buying a separate program such as AirFoil.
After connecting speakers to Airport Express, you need to run iTunes and click on a button in the lower right corner, which displays a pop-up menu for choosing where you want iTunes to play your music, either through your computerís speakers or through the speakers hooked up to Airport Express.
iTunes displays a pop-up menu in the lower right corner for choosing where to play your music
For extra flexibility, this pop-up menu also offers a Multiple Speakers option, which lets you play music through both your computer speakers and any speakers connected to Airport Express. By playing music through multiple speakers, you can have your favorite music playing in different rooms of your house.
USB port sharing
One handy feature of Airport Express is its ability to share any device connected to its USB 2.0 port, such as a printer. Printing wirelessly relies on the open source Bonjour software, which allows both Macintosh and Windows computers to recognize and use any printer connected to Airport Express.
When you print from any program, the Print dialog displays a list of all printers connected to the network, including printers connected to individual Macintosh computers and any printer connected to Airport Express. Just click on the printer you want to use and print as if you had that printer connected directly to your computer.
For its low $99 price, Airport Express is a simple and convenient way to create or extend your WiFi network. While its USB port sharing feature is nice and its WiFi Internet access acceptable, the most useful and distinct feature of Airport Express is its streaming audio feature.
If you donít need to stream audio, then an ordinary WiFi router might be just as easy to hook up and be even less expensive to buy. However, if you want to stream audio from your iTunes collection, then Airport Express will be your simplest and easiest solution.
Besides streaming audio, Airport Expressís second most useful feature is its small size and portability. Just plug Airport Express into any electrical outlet, set up Airport Express using the enclosed Airport Utility program, and you can create or extend a WiFi network in minutes. For streaming audio and portability, you canít go wrong using Airport Express.
Compatible with Mac OS X and Windows XP SP2/Vista.
Works flawlessly with iTunes.
Supports 802.11a/b/g/draft n standards.
USB port sharing.
Extension cord optional.
Audio connecting cables not included.
10/100 Ethernet port does not support the faster 1000 standard.
Only allows audio streaming from iTunes.