Specialcase got it. Motion 2 project files are treated as though they are QT movies by FCP (and DVDSP and After Effects). If you import the .motn file it will play like a .mov but you still have the ability to save changes in the original .motn file and have them update automatically in the calling program.
As Noah said, always try to judge things on a broadcast monitor, not the computer monitor. And per his suggestion, rendering the project as a QT .mov file will enable faster performance in the calling app. Changes to the original project would have to be rendered to a file with the same name as the previous render.
Jim Kanter,
Digital Film Institute
http://www.dfilminst.com