AirPort Base Station Firmware Update 7.6.4
Apple has released AirPort Base Station Firmware Update 7.6.4 to correct three specific issues on all 802.11n AirPort base stations (AirPort Extreme, AirPort Time Capsule, and AirPort Express). It fixes a problem that could cause an intermittent loss of Wi-Fi connectivity with iOS devices and addresses an issue that could cause an AirPort Time Capsule to report that the backup disk is in use. Additionally, the update fixes an IPv6 Tunnel error that was introduced with Firmware Update 7.6.3. You can update your AirPort base station using AirPort Utility via either your Mac or an iOS device (with the free AirPort Utility app installed). Click or tap the base station with a red circle sitting to its right, then click the Update button on the Mac or tap Version > Download and Install on your iOS device. (Free, 728 KB)
Updated my 1st gen Time Capsule and 2nd Gen Airport Extreme. Update went smoothly. I had not noticed dropped connections on iphone5. iPad mini occasionally had to re-connect when the 7.6.3 firmware was in place.
No problems at this time. Will post again if something comes up.
Apparently this update also included a fix for a DoS issue, but it's just now being announced...
Impact: An associated client may be able to cause an unexpected base station system termination
Description: An issue existed in the parsing of small frames with incorrect lengths. This issue was addressed by adding size checking to the parsing of small frames.
http://support.apple.com/kb/HT5920