Having been through a few courses where Lean Startup was the primary approach to new business/venture creation, this is super interesting. I think there is a time and place for Lean Startup - say you are entreprenuerial, but you don't have a real idea yet. Or your goal is to marginally improve an existing product or service. There is still plenty of appeal in creating a business in this way, but perhaps bigger, paradigm shifting ideas require less input from customers and experimentation.
Would love to get input from actual founders @Bill (not sure you can @ someone on Readup) on their take of Lean Startup.