There has been talk of 10x developers for as long as there has been software engineering.
I have had the good fortune to work with some profoundly great engineers, and it is fantastic.
But do you know what is much more motivating? 10x codebases.
The codebase you can’t fuck up because you have tests covering your ass.
The codebase you can add new features to without breaking step, because it was thoughtfully designed with change in mind.
The codebase you don’t have to wait for, because the build, test, packaging and deployment are automatic and rock solid.
Is the 10x developer a myth? Who cares. But we have all worked on 0.1x codebases. Do the math.
Mike Long's Blog 
Awesome post Mike. Only thing I might change is the title (but I’m not sure what too… 10 x what?). It’s not the codebase alone that determines its goodness. It is the system it lives and breathes within. As indeed you yourself write when you mention the tests that the code co-evolves with. And the building, packaging, deploying, etc are all automatic and rock solid.
Indeed Jon. The feeling I was trying to get across was that the environment (including the code at its centre) is the largest determinant of productivity in development.