Apple posts workaround for Macs that stop responding during setup
If you're having problems with the setup process hanging on your new MacBook, Apple has posted a support article today outlining a remedy.
The support article addresses a fairly widespread problem where setup stops responding and displays the dreaded "beach ball" after one creates a user account. If you're experiencing the problem, Apple recommends you either wait about 30 minutes for setup to resume, or complete Setup Assistant without connecting to the internet.
Full story from the iMore Blog...