However, I also put another amount, equal to about half my interest payment, into an S&P 500 index fund. It is automatically deducted from my account. I am doing that in lieu of my mortgage principal, as I believe that over time, the S&P will beat the mortgage interest.
Furthermore, the mortgage is less than 50% of the house's current value. It was about 55% of the value when we moved in two years ago, but I figure the house has appreciated somewhat, if nothing else than the fact that it has a new roof and boiler and basement floor and a bunch of other stuff we financed out of pocket to repair / upgrade.
You are probalbey in good shape, just because you are so upside on the mortgage. But there are people out there who owe 100% or more with intrest only loans because that is what they could afford. If this market goes south as I think it will there will be a lot of people losing their shirts.