My worst experience was with a Lowes washing machine. It stopped working correctly, called Lowes, they sent a technician a couple of days later, technician ordered a part, technician came back 3 days later to install part, still not working. Technician was going to "talk" to supervisor and try to come up with a solution. 3 days went by no news. I called Lowes again and they said they would have to send another technician to repeat the whole diagnosis process again. This was after several "4 hour" window "vacation" hours I had to use to be home. I told them I didn't want to go through the whole deal again and to see if I could get store credit and I would buy a new one paying the difference from the store credit. They said no. I told them to shove it and dont proceed with the warranty ticket. I have since "boycotted" Lowes.
2 weeks went by with no functioning washing machine (I know it isn't like an air conditioner being out but it was a major inconvenience).
Other than the washer, I had a lot of success with Lowes warranty in smaller items like Dremels, drills, portable air conditioners, etc)