Apple has, with no change in the release notes, released Thunderbolt Software Update 1.2.1 to add support for the Thunderbolt to Gigabit Ethernet Adapter. Version 1.2 of the update was notable for causing boot failures, and although the assumption is that Apple addressed the problems, we won’t know for sure until reports start to come in from users (see “Thunderbolt Software Update 1.2 Causes Boot Failures,” 12 June 2012). Happily — and unusually — Apple has acknowledged the problems caused by version 1.2 of the update, apologized for the disruption, and offered recovery information.
Although it will reduce the sample size of fresh installations, I cannot recommend that you install this update unless you have and need to use the Thunderbolt to Gigabit Ethernet Adapter for your MacBook Air or MacBook Pro with Retina Display (the device should work on any Thunderbolt-equipped Mac, but all other models should have a dedicated Ethernet jack). At least with what Apple is telling us in the release notes, the update has no other benefits.
While I don’t wish to denigrate what Apple has done here in terms of acknowledging the problem in public and apologizing for the disruption, since that’s such a refreshing change, I would like to point out that it took Apple several days to remove Thunderbolt Software Update 1.2 from distribution, during which time tens of thousands of Mac users could have wasted one or more hours each reinstalling Mac OS X. During those days, the word spread quickly via TidBITS and other Mac media sites, and via social networking, and although there’s no way to know how many people would have been affected, it’s likely a non-trivial number. In this day and age where the media appears to focus on rumors and controversy, this is an excellent example of the true value of an independent technology press.