This is getting way too off topic, but as with anything "it depends". Sometimes mortgage interest is your friend. At only 3.625% for a 30 yr fixed, I have access to hundreds of k of cheap money. A loan that the fed subsidizes down to a lower effective rate. In fact, without mortgage interest I probably wouldn't get over the standard deduction and be able to deduct property taxes or sales taxes. So its like I am borrowing for 2.5% or so. All I have to do is earn more than that and I am ahead. Since I actually have the cash, I will sit it in Lending Club (9%/yr) and have it make the payments for me. In fact, I project that in 15 years or so the interest portion might have shrunk too low and I might really need to refinance, pull the principal out and restart a 30 yr, assuming rates are good again then. Assuming you don't have house money in cash, it is still better if you have rock-solid financial discipline and invest the extra money you *would* have paid into a 15 or 10 year mortgage payment into something higher yielding (seriously, lending club) and using arbitrage to make money. If you let your sacred "house fund" compound the interest you will enough money to pay off the mortgage faster than a 15 year straight payment. However, 99.9% of people lack this discipline. The feature/flaw of mortgage principal is that it is savings that cannot be raided.
