Full disclosure- I'm currently in that program and loving it.
Once you're accepted though, you'll have to complete two foundational courses within a year (with a grade of at least B) in order to continue to be eligible. This applies to all new students.
From my own experience, some of the courses are pretty easy, so getting a B or higher isn't difficult.
It's not that rigid or difficult and carries no real weight.
You'll get as much if not more from the free machine learning Georgia tech course with Tom Mitchell's book than the nanodegree.
As a follow up, I took Thruns robotic driving course and it suffers from being a purely software course. There are optional hardware projects but no imparted hardware instruction.
So I'd be especially leery of an automated driving nanodegree degree online.