Feh! Other than the fact that AirPort Extreme Update 2007-004 [1] is available for Intel-based MacBooks, MacBook Pros, and Mac minis; that it "improves the reliability of AirPort connections," and that it's available via Software Update or as a 745K download, Apple isn't saying anything interesting. Oh, it also reportedly requires Mac OS X 10.4.10, and is available in English, German, French, and Japanese.
[1]: http://www.apple.com/support/downloads/airportextremeupdate2007004.html