I wore my watch for about an hour and while at work I felt a burning sensation on my left wrist. When I removed my watch the casing was warm to the touch and saw that the watch sensor burned my wrist. I got a blister and round red mark from the incident. Apple support said that their engineers found no defect with the watch (without inspecting it in person) and suggested I wash my watch band because I might have a skin irritation and to buy a plastic casing for the watch itself. WTF!