[nadam]

"What Ries and the Lean Startup advocate is picking an X value so that you have to build as little as necessary to validate your long-term assumptions. Neither the book nor the method prescribes whether the “X value” should be high or low on the spectrum. This decision is entirely up to you, influenced by your market and your criteria for evaluation."

For exactly this reason, although the lean method still works, it is no longer a 'revelation' or an 'edge'. It was a revelation when the cost of validation was low. Now using the lean method is just a triviality: you constantly need to validate your ideas. As the cost of validation increases dramatically the importance of other success factors (like insight, strategy, deep knowledge) increase.

[mikehollinger]

Y - the concept of frequent validation differentiated the stuff I’ve worked on that’s done well from the stuff that didn’t. Put a different way: the items that we didn’t get good validation on had to landed with a thud in market, or needed to make sizable changes before they were accepted. The items we validated effectively had to make the same changes, but we got there in smaller steps with less pain.

Also: don’t forget business model validation. Having great tech that sellers won’t sell, or customers can’t buy is a tremendous waste.