watchOS 2 Beta 3 is considered a minor update, since it only features bug fixes as well as under-the -hood improvements. Although watchOS 2 is indeed the first major software update to hit the Apple Watch, which will enable devs to build native apps that can run directly on the smartwatch itself instead of the iPhone, as well as granting them even more access to the watch's hardware such as the taptic engine, sensors, microphone, and much more.
You can get watchOS 2 Beta 3 through Software Update from an iPhone running iOS 9, by going to the Apple Watch app > General > Software Update for registered devs.
