It looks like Apple has added a new feature to the Airport Express. With the 6.3 Firmware Update, it is now possible to stream music from iTunes to more than one Airport Express simultaneously. So if you have more than one Express in your home, and they are hooked up to stereos, you can essentially broadcast your music throughout the house.
From the sound of it, Apple didn’t stop there. It is also possible to play music on your Mac’s speakers at the same time as the Airport Express. This makes for an ideal feature that I could have used hundreds of times.
The surprising part is that Apple has done little to publicized the update. One of the key selling points of the Express is its ability to stream music. This firmware update greatly enhances the Express and makes it dramatically more useful. Only a brief mention on the update Airport Express page at Apple indicates the new functionality.