I also think his upfront time estimates were off. He estimated Ruby to be ~15% more productive than C. I don't write Ruby, but I do write a lot of C and Python.

I also think his upfront time estimates were off. He estimated Ruby to be ~15% more productive than C. I don't write Ruby, but I do write a lot of C and Python. I'd estimate that it takes 5x less time for me to write a program in Python than C. Even if the 5x number is off, it's still a way larger reduction factor than 15%!