I'm working on some educational Scala project. And IDEA is natural choice for that. Normally I use Emacs for my work, but for anything Java related it's not as good as IDEA. And I cannot express how powerful and polished this nearly free software IDE is.
However, I was missing one very useful feature of Emacs, which is ability to open several frames to effectively use two monitors. Until few minutes ago.
When you want to open same "buffer" on two monitors you can first split it horizontally (C-x 2 if you use Emacs key bindings) and then you can simply drag one of the windows out of it's frame to second monitor! If you want different files you can just drag tabs out of main frame.