If you’re using a Mac then AirPort Express' setup process is almost insultingly simple. AirPort, Apple's network configuration utility, is built into its OS and as such all that's required is to find a spare socket for the AirPort Express, before connecting your system to it and following the simple step by step instructions to configure the wireless ID, security and encryption settings. On a PC it's no harder, so long as you can cope with installing the Windows version of the AirPort utility.
Connecting a printer isn't difficult, either. Suffice it to say that as long as you can cope with the setup process without AirPort Express getting involved, you'll also have no problems when it is. I'm not entirely convinced this is functionality that a great many people want given the vast number of networked printers around, so it's not likely to be a selling point, but it's there if you want it.
A notable feature available to AirPort Extreme, the big brother to AirPort Express, but missing here is the ability to connect a USB hard drive that can then work as a Time Machine backup location. In fact, if you want that feature but don't want wireless music streaming, then a Time Capsule might be a better solution as it is basically an AirPort Extreme with a built-in hard drive.
Of course, it's a bit redundant to point out that you shouldn't be looking at AirPort Express if it doesn't suit your requirements - you don't need me to tell you that. Rather, what I should be assuring you of is how well (or not as the case may be) it does the things it can. And, as I've already pointed out, it does them with aplomb.
If you have a straight dsl/cable modem or a router without wireless (or one that only offers the older, slower, 802.11g standard) then the AirPort Extreme will 'n-ify' your setup nicely. Similarly, if you like the sound of streaming music from your PC to a different location in your home wirelessly then this is an excellent way of doing so on the cheap.
If the rumours that Apple is planning its own Napster or Spotify-esque music streaming service are to be believed then AirPort Express could get even better, too. Even as it stands, pumping out purchased or ripped tunes, Internet radio and Podcasts into the living room from my PC in my bedroom, controlled with my iPhone in the kitchen is undeniably cool.
As a wireless adaptor, Draft-N or not, AirPort Express has a compact, well thought out design, but that's not really enough to sell it. Luckily, the addition of a USB port and an audio output make this more than a one trick pony. You only have to start streaming music around your house to wonder why you didn't do so sooner. Only the price could be prohibitive.