A fairly exhaustive breakdown of everything new in FCPX version 10.1 by the well-known Philip Hodgetts (maker of several important and needed plugins for FCPX) they squashed all the bugs his team had found and launched tons of new features.
Overall, this is a huge improvement to FCPX, and ton of little detailed fixes and advances. The biggest change that needs to be pointed out is that Apple has restructured the event/project entirely into a new thing called “libraries”. Gone is the old home-pane with a set of timelines at the bottom representing the “projects” you had. Libraries contain Events. Events can contain Clips or Compound Clips (as they do in earlier versions) but also an Event can now contain a Project. Projects are no longer separate from the Events they work with.
My first dive into it without reading anything was very strange and disorienting. You need to read this breakdown or search for Larry Jordan’s videos on it.
One of my favorite new features is an ultra fast way to save a version of a project, called “snapshots” with a simple key stroke you can save a time-date stamped version of your project as it presently is, that you can go back to later. I do this frequently as I build complex projects or non-story work that often has version with many changes and the need to jump back in time to grab things I’d done before but cut out.