FCPX frame rate conform

   Frame rate conforming cannot be easier in FCPX:
- Bring your clip into the Timeline. (29.97fps clip into 25fps Timeline for ex.)
- Select the clip, then go to the Inspector (+4)
- Under Video > Rate Conform, select Frame Sampling = Frame Blending or better yet Optical Flow.  The later takes longer as FCPX needs to analyse the clip first.
Done. And it looks pretty good!