A Question on British Usage

Is there a serious difference in meaning or connotation between being "mad" and being "daft"? Neither word is common usage in the United States; we tend to use "crazy" most often. I have always liked the word "daft" though I never use it because it would seem an affectation, or quite simply because no one would understand what I meant. (Malkhos, however, never worries about being understood. The people who need to understand, will; the others are irrelevant.)