I never had any problems with the volume slider whatsoever. Never bumped the volume more than I wished, never did the piece fall of. I think people just want to nitpick and find problems where there are none. Sure, say about the battery life (which is the same for many other high-end DAPs) or the lag, but the volume slider imho is perfect.
I read the same article and I was certain that he was going to mention the battery life as the dealbreaker.