Summary
The AirPort Express certainly has a lot to offer in a small package, but the device's practicality may be relative only to a small subset of users. Those that specifically want to use iTunes for their music streaming and don't mind having to use their laptop will find the AirPort Express useful. Those that don't have a wireless network and only want wireless clients (10 or less) may also be interested in the product. The device may be perfect for those that live in a small apartment or dorm room and don't want a wired network and don't mind having their stereo in the same room as their printer. But if you plan on using all of the AirPort Express' features, or already have a wireless network, you may want to reconsider.
And while Apple wants you to believe that the $129 price is a steal, keep in mind that the package does not include any connectors for audio or Ethernet and the connection pack is an additional $39. It seems to us that you are paying a premium for the Apple name in a product that is certainly unique, but just may not be practical for many users.
The AirPort Express has an acceptable wireless range and speed and, for the most part, is easy to set up. It also does a good job of printing with supported printers and playing iTunes music. There's no denying that the AirPort Express mostly works as described by Apple, the problem is that its uniqueness might overshadow its actual usefulness.

The AirPort Express certainly has a lot to offer, but the device's practicality may be relative only to a small subset of users.

by John Evans on November 8, 2009:
“The Apple Airport Express works extremely well even on Wireless G. Unlike most network media players, playlists remain on the host computer (iTunes). Thus large playlist data files don't need to be analyzed by the media player, and that can cause lag especially...” More...