It will change the keyboard commands to those of FCPX *IF* there is an applicable similarity in functionality -- example: the Q key just gets turned off since there is no storyline analogy in Motion (Q selects the 3D transform tool). In Motion's standard set, typing the K key will create a Clone layer from the selection. With the FCPX set, it becomes the Stop key in the J,K,L rewind/stop/play sequence of keys (useful, but the period has the same functionality as J and the comma the same as L -- advancing one frame in reverse or forward direction). However, double-tapping the J or L keys does not speed up the playback in Motion (in FCPX, you can tap the J and L keys up to 5 times [I think - or MORE!] to increase the speeds 2x, 4x, 8x, 16x and 32x ... )
Also, if you use keyboard shortcuts to get to the various tools, switching to the FCPX set will pretty much bash all of them. You can reconfigure all the Motion keyboard shortcuts you use mixed with FCPX shortcut keys if you want to take that much time configuring a custom set (Duplicate first!) It would be more useful if there was a more convenient way to switch between the two sets rather than having to go to the menu, but for the most part, I don't see the point.