Rating: 5 / 5
Upon receipt of the pad, I inflated it to sleeping firmness, and stood it up against the bookcase. An hour later it looked rather soft; three hours later it was in a pile on the floor. Brand new, and it won't hold air. Be sure to test yours before you depend on it in the woods!
Update: I ordered a second X-Lite, and after 48 hours it appeared that it had a slow leak. However, upon further investigation, I determined what had appeared to be a low leak was in fact my dog knocking the pad over so that it appeared to have collapsed. At this point in time, the pad has held the same level of air for nearly a week. I'm satisfied, and have changed my rating above to a 5.