I recently updated to the newest Apple Airport Extreme 7.6.3 Firmware on my base stations, nothing noticeable. Here is the change log.
About AirPort Base Station and Time Capsule Firmware Update 7.6.3
- The ability to extend the Guest Wi-Fi network on a network that is configured with multiple AirPort Base Stations
- The ability to add a WPS-capable Wi-Fi printer
- Improved international support