cooper.com
Lean is the opposite of what they preach. They are very much the big up front design. That is what pays their bills.
Plus he is as much aiming at designers as he is at developers.
Perhaps it's different for designers, but my experience with people in other areas is that people get trapped in a learn > learn infinite loop.
So one of the advantages of the Ries cycle -- build > measure > learn -- is that you gain a critical bit of forward momentum right at the start.
But it's very important to understand that it's not enough to divide and conquer you will have to put together the right kind of personalities.
I don't agree with their 3 day cycles it's still problematic because it keeps the design from the actual end customers.
You need to get to launch before you start to seriously think about iterating.