ALT+` switches windows within a running application.
But I notice that you actually have to press this key combo twice to switch to the next window. Pressing it once only displays the application's open windows (within the current workspace).
Why is this? Why isn't a single ALT+` sufficient to switch windows?
After all, ALT+Tab behaves in the expected way when you want to switch between applications.
I'm running Ubuntu 12.04.