I disagree. There's simply no way that the IDE can know everything about a variable without running the code and I don't believe that eclipse does this.
It's ok at refactoring but it breaks down all the time for me, renaming unrelated variables or missing cases. I don't believe it can handle kwargs for example (no computer in front of me, feel free to prove me wrong)
In theory, you're right. In practical, day-to-day programming, an IDE can get it right the vast majority of times and do exactly the right thing. See a previous post of mine: http://news.ycombinator.com/item?id=4037602
I believe that "works almost every time" is great, but that last inch is also meaningful. Knowing you can trust your IDE's refactorings is reassuring and allows you to dare do things you might otherwise not dare.
It's ok at refactoring but it breaks down all the time for me, renaming unrelated variables or missing cases. I don't believe it can handle kwargs for example (no computer in front of me, feel free to prove me wrong)