I don’t know about you, but when I copy something to my clipboard, I tend to hit ⌘-C about two or three times out of habit to make sure that I really copied what I wanted. I think it’s because there’s no great visual feedback that my command was executed. Sure, I might be able to catch the Edit menu highlight for a second, but my attention isn’t usually there, and the menu could even be on a different monitor.
What would be really useful is just a small pulse of the highlight to let me know that what is selected was just copied. If you make an OS, please steal this idea.
I used to be the same about saving, but then Apple added a nice touch to their (lowercase) windows.
This is what the upper-left corner of a document’s window looks like when there are unsaved changes. See the dot in the center of the red close button? That lets you know, before you close the document, that not everything is saved.
It’s nice, because when I hit ⌘-S, I only do it once and can tell at a glance that my edits were saved successfully: