[AmericaUnited]

That is, if you have a mortgage with 6.5 percent interest, you'd earn roughly 6.5 percent by paying it off early.

Actually it's worse than that for most people because that interest is tax deductible. So you're getting more like a 4% return. NOT THAT GREAT!

[BenLurkin]

Except there is no point in paying interest to the bank just in order to get a deduction. There are other ways to shield that money and still keep it. A person paying off their mortgage could turn around and fully fund a 401k plan and thereby reduce his or her tax liability.