Motion is also an effective basic 3D compositor, with controls for setting layers in three-dimensional space and adding lighting and camera controls. 3D compositing is powerful, though if you need native support for stereoscopic 3D output, you'll need to look elsewhere. Also, one potential downside of the reliance on the GPU is you can get different results on different hardware; the only bugs I encountered were a couple of non-reproducible Nvidia GPU-related crashes.
As before, Apple also bundles a great deal of functionality and content in the box. You get sophisticated, easy-to-use match move and motion analysis and stabilization features, inherited from Apple's high-end (and now defunct) Shake product. 3D compositing includes the ability to quickly rig up a scene with depth, then add movement simply by dragging and dropping simple motion behaviors. There's a powerful, intuitive replicator and particle generator that with After Effects, for instance, would require a third-party add-on. Apple has also bundled a vast library of preset content.
Advanced After Effects users will often (rightfully) praise the Expression scripting language, which allows users open-ended extensibility by enabling advanced motion behaviors in code. Motion's approach is visual rather than textual, but it should not be discounted. By combining behaviors, generators, and filters graphically--spreading them out across the timeline, and adjusting parameters on the fly--it's possible to build more complex structures.
As before, any slider, anywhere--from a crop control in an image to the amount of a filter blur--can be manipulated or controlled with keyframes, audio, and even MIDI controllers. (Most audio control hardware transmits standard MIDI messages, so you could, for instance, assign the level of an effect to a knob or key on a keyboard.) What Apple has added to Motion 5 is the ability to encapsulate selected controls into dynamic parameter rigs, controlling many elements at one time. That's useful both in the context of Motion itself, and as a means of exporting smart templates and interactive visual materials to FCP X.