This is great news!! For the uniformed, PMI (private mortgage insurance) is insurance YOU would have to pay as a home buyer for the benefit of the lender/mortgage company in the event you are putting less than 20% down. The fees for this can be pretty hefty.
Now, some lenders are actually offering borrowers with good credit the opportunity to borrow up to 85% of the sale price (15% down), with NO PMI and the exact same interest rate they would get with 20% down. For these same high credit score borrowers (generally this means over 700) they can put even 5 or 10 % down and not pay ANY PMI, but at these lower down payments they can expect a small rate bump - on the order of 1/4 point.
Buyers with less than stellar credit are also eligible for slightly higher rate bumps, but NO PMI means the savings are still huge! This is a great deal!