Personally, I think they should have replaced the phone under warranty. Cracking around the ringer/silent switch is a known issue, and I only found out after I replaced it that that switch is also known to break off. I could have spent hours on the phone with Apple to berate and cajole them into doing the right thing, but it would have been an uphill battle. And it probably still would have resulted in my shelling out $200. Not too mention much angrier.
One thing I have noticed with the replacement that some of the apps still start spontaneously, so that clearly is a design problem. I don't know if the software can adjust the motion detectors not to trigger apps that I clearly did not start. It's not as common as it was.