What is a Notes Day and can it be used in DevOps transformation?
I see some interesting parallels in this story and The Phoenix Project.  (Spoilers ahead for the book, if you haven't read it read this anyway :))

I take it the title for "Notes Day" comes from the term of art in Hollywood, where "notes" are constructive criticism about a work.  In this story, Catmull plays the part of Parts Unlimited CEO Steve Masters.  Catmull accepts that he can learn from his employees how to do a better job, as Masters does in Phoenix Project when he does his public mea culpa and apologizes to Bill Palmer.

In a sense, Catmull is also Brent- he's a major constraint.  If his time was so precious, it meant that Pixar was struggling to delegate authority.  It seems  Catmull was critical to every decision, rather than able to set large-scale goals and leave it to employees to figure out how to achieve them.

An event like this might work well at some companies, less well in others.  I think it's the key idea behind Notes Day that is most valuable: accountability and transparency from the highest levels of management to the last employee.  That value can be spread throughout a company in a variety of big and small ways.