I've been lamentng threading issues in Windows IDEA 64-bit since v10 was released. A simple Rename refactoring would send IDEA into a thread deadlock that took 2 - 5 minutes to unblock. Same for Extract Method, Pull Up, etc. This productivity killer drove me to do my heavy TDD refactoring work in Eclipse. I'd go back and forth, staying mostly in IDEA for editing and testing and Eclipse when doing refactorings to avoid the threading issues in IDEA.
Today, I was going to refactor some common code into a new class. So I started up Eclipse, then started IDEA. I got the notice that 11 RC was available, so I thought, "Why not try it?," so I downloaded 11 RC. And I'm glad I did!
All of the refactorings I invoked responded nearly instantaneously, with no thread deadlock. (The first time I did a Pull Up Members may have been an exception, but after the first time, it, too was speedy.)
I haven't tried all the refactorings I normally do, but the most common ones. All were very fast! Same with the quick fixes.
However, I did find some bugginess that I've reported in YourTrack. For instance, when renaming a method, IDEA renamed the class. :O
All in all, I'm very happy to see that the threading issues are being fixed!