We paid extra on our 15 year mortgage every month. It was auto deducted from my checking acct but I just told the bank to add an extra $x to principal (do it in writing). We did this for six years and it really has helped with our equity situation now that we are selling our home.
DH and I decided to pay extra because we could and instead of having $1025.62 taken out of my account, it looked nicer to have an even $1100 deducted every month. At the time, we escrowed our insurance and taxes but no longer do that so we earn the interest and not the lender.
With our new house, I'm not sure what we are going to do. We have an interest only loan for now until we sell our current house. Based on our down payment from the sale of our house, we are really trying to do the 15 year mortgage again. We don't need any of our equity to fix up the new house b/c we bought a move in ready home (with a new roof, new HVAC, new kitchen, new electrical, new paint, newly refinished wood floors), unlike our current home which we had to put about $30,000 into in repairs and updating over the past 10 years. If we can't do the 15, we will try for 20 (yes, they are out there) or 30 as the last option and pay extra in principle each month.