[quicksilver03]

They have already implemented it in IDEA 12, if I'm reading their website correctly.

Which personally I think was a waste of development time, I cannot imagine how it could be useful to keep compilation errors in your code.

[ngd]

I tried it out, you can now make an Eclipse like experience, albeit requiring many key presses to invoke compiliation and execution of code. It's not as slick as Eclipse, but its possible.

As for the merit of the technique - try it out. I've found it allows a level of experimentation not possible without the option; personally I've found that useful when it is not obvious what the right thing to do is upfront, I can try out a small change to a chunk of code, try it out via unit tests, then update all call sites appropriately; as opposed to attempting to "upgrade" call sites appropriately using a canned refactoring before I've validated whether or not I'm going to be able to achieve what I want for a few test cases.