I don't believe their "lifetime replacement" warranty covers any sort of power tools, just the hand tools.
On a lighter note, I once found a pair of Craftsman needlenose pliers in the street. They had the crap beat out of them, they were rusty and even the rubberized grips were pretty much shredded. Took them to Sears, just to see if they would replace them....they did, no questions asked. COOL!!!
Randy