We recently noted Apple's release of AirPort 3.4. Apple also released AirPort Extreme Firmware 5.4. Available for both AirPort Extreme Base Stations and AirPort Extreme cards, it provides "improved antenna output control, enhanced logging from your base station which is compatible with syslog, and performance improvements for WPA security implementations."
Apple also recently posted, then removed, a new AirPort Management Utility 1.0 page. Knowledge Base articles discussing the utility now note "AirPort Management Utility 1.0 may be found on the software CD included with the AirPort Extreme Base Station (PoE/UL 2043)." However, you can still download the software from the AirPort Support page.