This is general for Yosemite, but I choose an example from Mail to descibe what I mean: Before Yosemite I could start writing the recipient *directly* after I hitted COM+N. Now I have to wait a while before Mail respond to what I write. Like the OS doesn't accept me writing if it's doing something else (like creating the New Mail window etc). This slow responce is visible everywhere since Yosemite, but it's easiest to observe in Mail. This is not acceptable. It disturbs my work speed. More than one could think... Any ideas how to avoid this?