FCP X version 10.0.8 is mainly a maintenance release, but it does add a couple of features.
Users of Arri Alexa cameras can now record Apple ProRes with Log C video levels, then view with standard contrast and colour levels in Final Cut Pro X. This non-destructive display option lets you view footage in the Rec. 709 colour gamut (the standard for broadcast video - pictured above) without having to render or apply an effect, while accessing the full dynamic range of Log C (which has so little contrast it almost looks foggy - as seen below) for colour grading and compositing. When editing is complete, export XML from Final Cut Pro X to send the Log C files for finishing in third-party applications such as DaVinci Resolve or Autodesk Smoke.