Black halo / ghosting on transparent layered PSD file imported into FCPX
As Final Cut Pro is not made by Adobe, it does not have the same exact processing engine for dealing with the effects in a PSD.  This appears to be an artifact of the difference in processing between the systems.

To work around this, I would recommend exporting the components as TGA or some similar file format that has alpha support.  Simple alpha blending is far more likely to blend in a predictable manner between applications.