Final Cut Pro X 10.0.3 update released Jan 31st supports Multicam Editing, Broadcast Monitoring, Photoshop layer import, advanced chroma/green screen keying, media relink and XML 1.1 for Davinci Resolve for grading and colour production workflow.
Focusing for now on the multicam addition, in short it means that when you shoot with two or more cameras you can switch between them whilst editing. See video demonstration below.
New innovations include using video and photos using time of day metadata on your files for synching, also you can shoot with different types of HD cameras, format, codec and resolution, this was previously unavailabe in prior versions of Final Cut Pro.
First users will see the muliticam option as shown below
The Multicam Clip option in drop down provide the follow synch start for video.
Play back multiple angles at once in the customisable Angle Viewer window, plus with powerful new Angle Editor goto any Multicam Clip and make precise adjustments.
So you can for example synch and edit, mutlicam footage and photos from a DSLR, iPhone/mobile phone video and a HD camera, playing them back in realtime on your timeline.