Rest in peace, iPhone 3.1. It was just last month that the most recent iPhone update hit the streets and already it’s been superseded by the younger, faster, better-looking iPhone 3.1.2 that Apple released on Thursday. Whither iPhone 3.1.1? I’m afraid we may never know.
iPhone 3.1.2 appears to be focused mainly on providing bug fixes for a few problems introduced in iPhone 3.1. Apple specifically calls out a problem where iPhones may not wake from sleep—it remains to be seen if this is the issue that some users had dubbed "coma mode". In addition, the update fixes an intermittent issue that could interfere with cellular network services and require a restart, and a bug that could cause a crash while streaming video.
Once you update to 3.1.2, you'll also be able to download a new carrier update, though what exactly that's for we don't know at this time.
The update weighs in at a hefty 306.2MB on my iPhone 3GS, and is also available for the iPhone 3G, the original iPhone, and the iPod touch. As always, it's available only via iTunes.