Apple has released the golden master version of iOS 4.3 and Xcode 4 to developers. iOS 4.3 includes personal hotspot, a faster Safari engine, new AirPlay features and more. iOS 4.3 launches March 11th alongside the iPad 2.
The GM, is the last step before a new iOS version actually gets released to the whole world. Of course, this time we already know when that will happen -- next Friday, on March 11.
Sadly, there isn't anything new available for Apple TV yet. For now, this update is limited to the iPhone 4, iPhone 3GS, iPad, and iPod touch 3rd and 4th generation.
Still, if you're a developer, you're probably very interested in getting your hands on the pre-release versions of the OS and SDK, so go get them and start optimizing your apps for the latest version of iOS! Or you could start playing with the new functionality in iOS 4.3, such as iTunes home sharing, and, for the iPhone, the Personal Hotspot.