[loup-vaillant]

How do you measure your productivity? One would naturally tend to count the number of lines changed, added, maybe removed. But they are a poor proxy. What really matters is the value brought to the customer, and the cost of this value to your company. These are obviously very hard to measure at the programmer level.

I think the important question here is, does IntelliJ help you simplify existing code? Do you routinely simplify existing code? Does your team routinely simplify code? Or even better, does IntelliJ help you write simpler code in the first place? Meaning, is code written with IntelliJ routinely simpler than code written with Eclipse or Emacs?

My experience with IDE overall, is that they are of tremendous help for navigating complexity. On the other hand, they are of very little help for reducing complexity. (You cite the method renaming as an example, but compiler errors keep track of broken references just fine)

Regarding the REPL, it's not the REPL itself which is essential. It's the tight feedback loop. There are other ways to provide such a loop. Some of them are much, much better than REPLs: http://vimeo.com/36579366