Mine isn't slow. I don't understand how it's clunky. It seems secure enough to me. I have no problem. Whats the point in customizing it? Is that the only reason you get anything else?
Okay then, anything earlier than IE9 is slow, clunky and insecure. IE9 is not as good as the others, but at least it's useable.
As for customisation, it allows you to change quite a lot of stuff in your browser; you can modify the UI to your liking and add extra features such as ad blocking (INCREDIBLY useful).
