Well, that was fast. Since its launch last September, Apple's iTunes Radio has jumped into the number three spot among music streaming services. Not bad considering only iOS devices running iOS 7 can access the service. Its benefits are many: With more than 25 million songs, iTunes Radio has the largest catalog size of any service. Featured Stations provide an additional source of discovery, beyond simply building a station around your favorite song, artist, or genre. If you're already on an iOS 7 device, iTunes Radio is no-brainer to take for a spin next time you're in the hunt for tunes.