As predicted, Apple announced their new 802.11n Airport Express.
Now featuring support for the faster 802.11n Wi-Fi specification, the new AirPort Express Base Station delivers up to five times the performance and twice the range of the previous model. The world’s smallest 802.11n-based mobile base station, the new AirPort Express offers a great option for anyone who wants to set up a high-speed wireless network, share a printer wirelessly, or stream iTunes music wirelessly from a Mac or PC with AirTunes. And because its so compact, you can take AirPort Express with you and set up an ad hoc wireless network in your hotel room.
So the main difference is the 802.11n speeds which is welcome.
Interestingly at the time of writing the 802.11n Airport Express was not available in the UK online Apple store, but that might be just because today is the day of release.