Motion 5 is stupendous on its own, but the interaction between Motion and FCPX is way beyond my hopes. This is a must have for anyone using FCP in any serious way. BTW, get some training otherwise its really easy to miss a whole lot and there are features that must be done a certain way otherwise you can get really lost and frustrated. Conversely, Its quite intuitive if you understand what you really want to do, and how Motion works to accomplish it.
CalgaryCA about Motion, v5.0