What I am impressed with is that the audio playback does not have any kind of delay over the network. You can verify this as is possible to play itunes through multiple speakers, so if you have the computer speakers and airport express both sending out sound, the output is perfectly in sync. I'm surprised since most digital equipment tends to have some inherent delay, so well done Apple!
If you've bought yours second hand like I did, make sure you update the firmware (7.4.1 at time of writing) as I did have a few problems when it was on 7.3.2. Also you may want to use the Manual setup option to set the IP address as it tried to grab the same IP my PC was using, so caused a conflict on the network.
One other thing, if you plan having this in the kitchen next to the microwave, when the microwave is on it will interrupt the signal enough to lose connectivity. So if you can place it a good distance away.