This new AirPort firmware update contains versions 5.7 and 6.3 for the Extreme and Express base stations, respectively.

It addresses reliability and resolves issues with AirTunes, AirPort compatibility, and issues with some third party Routers.

Fixes:

-Resolves issue with Audio dropout when playing to AirPort Express with AirTunes
-Resolves issue with Wireless Disabled mode for AirPort Express
-Resolves issue with AirPort Extreme LAN Performance
-Resolves issue when enabling AOL Parental Controls
-Resolves issue with vulnerability to Denial of Service Attacks (bonk)
-Resolves issue with wireless internet access through AirPort via some PPPoA DSL Routers
-Improved reliability when printing through AirPort base stations
-Improved support for RADIUS servers
-Improved support for Network Time Servers (NTP) for AirPort when using an IP addresses

For the latest information on AirPort software, check Software Update in System Preferences or the following Apple websites:

Apple AirPort Express website at www.apple.com/AirPortexpress
Apple AirPort Extreme website at www.apple.com/AirPortextreme
Apple Support website at www.apple.com/support

Internet service provider (ISP) compatibility:
Internet access requires a compatible ISP; fees may apply.

For more information on using AirPort Extreme or AirPort Express with your Internet account, contact your ISP or go to the AppleCare Knowledge Base at: www.apple.com/support

Apple are giving much better descriptions of updates now a days.