Summary: Refinancing your mortage to a 15 year will usually save you on interest, and also force you to pay your debt down earlier. There are some things to look out for such as pre-payment penalties, and the fact you are locking yourself into a higher monthly payment. You should also factor in closing costs. You don't need to switch to a 15 year mortgage to pay your house off in 15 years, consider doubling your mortgage payment each month.
