Another six days have gone by, and thus another pre-release beta
of the forthcoming 10.8.4 Mountain Lion has been seeded to developers for testing. The new build, 12E40, again
lists no new changes or known issues, and asks developers to focus on the same areas as before: graphics, Safari and Wi-Fi performance. While not mentioned in the notes, the upcoming update adds support for the emerging 802.11ac
The 802.11ac protocol is a successor to the existing 802.11n standard, though the former had not yet been ratified even though the standard is now complete (a similar situation occurred with 802.11n, with products available years before the standard was finally ratified). While no Mac or iOS products currently support 802.11ac in hardware, expected revisions and updated products (such as the rumored MacBook Pro and Air refreshes thought to be announced at the Worldwide Developers Conference in June) may do so. Once widespread, 802.11ac should result in faster network speeds and greater range using the 5GHz band currently employed by 802.11n.
Earlier builds of 10.8.4 were also known to slightly improve battery life and address bugs with Wi-Fi stability and reconnection after waking from sleep. No timeframe for a final release of 10.8.4 has been given.