Apple has just released OS X Mountain Lion 10.8.5 which fixes AFP file transfer speeds on 802.11ac, as well as several other issues.
What’s New In This Version:
The 10.8.5 update improves the stability, compatibility, and security of your Mac. This update:
• Fixes an issue that may prevent Mail from displaying messages
• Improves AFP file transfer performance over 802.11ac Wi-Fi
• Resolves an issue that may prevent a screen saver from starting automatically
• Improves Xsan reliability
You can purchase OS X Mountain Lion from the App Store for $19.99 or update your OS by selecting Software Update from the Apple Menu at the top left of your screen.