In the FWIW department…
I have only used Migration Assistant once, and that was to migrate the data from a PPC DP/800 to an Intel 24” iMac core 2 duo (2.33 GHz).
While the procedure was not, in absolute terms, flawless, it was sure close to it. A few applications needed to be reinstalled and in a few other cases, serial/registration numbers needed to be reinput. Aside from that, all was perfect.
In a subsequent discussion with an Apple Genius, he (unofficially) suggested doing an Archive and Install (while saving settings of course) immediately after using MA. That way, you can ensure there is no damage to the OS as a consequence of using MA. How valid that argument is, I dunno. Maybe your son can check that out.
And finally, when I first ran DiskWarrior on my new system, there was much to be fixed, even though I ran it just prior to using MA. Nothing major was found and all discrepancies were repaired according to plan. Still, ‘tis probably worth doing (IMNHO).
Enjoy!