Microsoft has officially launched Windows Phone 8, the next iteration of its mobile operating system. At an event in San Francisco, the company publicly showcased the final version of its new OS running on a variety of handsets from Nokia, HTC, and Samsung. Microsoft also used the opportunity to announce the pending arrival of Pandora and other high-profile apps that have thus far been absent from its platform. Windows Phone 8 handsets will begin appearing at retail over the coming weeks, but until then we've gathered all of today's important news for you in one place.