It is nice, but to my mind, a slider is different to a switch. The classic "on-off" switch that the author takes on is like a light switch - to that end, it does its job pretty well, I think, telling you what state it is in.
I don't know about you, but I rarely look at the labels on a light switch. When I find light switches that go side-to-side, I usually have to rely on my knowledge of the current state of the light rather than the position of the switch. Either way, you have to agree that the confusion the article speaks of is a reasonable one, and making interfaces that are resilient to be confusing is the job of the UI designer.