I understand this is quite late to the party but here goes my 2 cents: Machine-bound challenge-response is treacherous territory for digital nomads like me, or simply, for people whose studio lives on their MacBook Pro. Those things fail routinely (some component or another) and guess what Apple does? They just swap out the logic board and put in a brand new one. Once that's done, though you might still have the same machine, serial number and physical warranty speaking, all the parameters that the Machine-bound challenge-response mechanism rely upon have been swapped for new ones. Same machine to us humans, not to the mechanism.

Had this issue two laptops ago with Eventide - iLok wouldn't 'release' at least one of the licenses for the 7 plugins I bought from them, they said: Take it up with Eventide, and Eventide - well, you can imagine what they said.

Ideally, a single interlocutor when it comes to licences is preferred - no matter the mechanism. And then there's the matter of either the iLok or laptop itself getting stolen - but knock on wood I've not had the misfortune - nor do I plan to.

I hope that feedback helps!