Apple has released an update for all "late 2012" Macs which improves compatibility when using the 5GHz band in Wi-Fi. The update weighs in at a tiny 1.49 MB and requires OS X 10.8.2. Users can download it via Software Update or the link below.

Mac Wi-Fi Update 1.0

This update is recommended for all late 2012 Mac systems. This update improves compatibility when using the 5GHz band in Wi-Fi.

Boot ROM or SMC Version Information: To confirm the update has been applied, the CFBundleVersion string of the AirPortBrcm4311.kext will need to be checked.

New driver delivered in update: AirPortBrcm4331.kext CFBundleVersion = 612.20.15

/System/Library/Extensions/IO80211Family.kext/Contents/PlugIns/AirPortBrcm4331.kext/Contents/Info.plist