Really relieves the headache of going back and forth between tabs and windows copying and pasting one thing at a time. Copy images, plain text, links, etc. You can even tell it what kinds of things you don't want copied (e.g., passwords, etc.).
A good improvement would be made by adding a little quick response like changing the shape of the mouse or something else nearby. That would tell me clearly whether I have just copied something or not. The sound of copy acts very unreliable, and annoying when I listen to some music or working in a quiet place. It's a stupid design which fails.