The problem that drives me nuts is that when I switch languages by pressing Cmd+Space it does not switch if I press it too quickly. It's the same with Caps Lock, too. The system simply does not respond to the key-presses that are too short. This is not a bug, it is by design. The problem can be solved by switching on the slow keys (System Preferences > Accessibility > Keyboard > Hardware) and setting the acceptance delay to the shortest option. Then I can switch the language as fast as I like and the capslock responds accurately, too. But then the key repeat speed setting (System Preferences > Keyboard) stops working (I prefer the fastest), and it is a pain to move the cursor while editing a text.
Is there a way to edit the Defaults or something to have low acceptance delay and high key-repeat speed at the same time?