The author does a good job of pointing out the weaknesses of the experiment in question, but provides no real arguments as to why its conclusions couldn't be true. In fact, this is all he really gives us:

"Here, I just flatly disagree with the implication that someone would enjoy this “kind” of story more if they already know the ending."

and:

"...the best way to enjoy the “Twilight Zone” episode “Time Enough at Last” is to have no knowledge of the ending."

In other words, "you're wrong." Flat out opinion with no supporting rationale. Furthermore, he accuses the study of only taking one kind of enjoyment into account, when it seems to me that he's the one guilty of that. He says:

"...but that enjoyment is simply not the same as the intended enjoyment."

It appears that he's saying, "there is a right way to experience a book." The study (as far as I can tell) just asked people which version of the story --spoiled, or unspoiled-- they preferred. People can prefer things for a thousand different reasons.

Anyway, I agree with the guy that this study should not by any means be regarded as the final word on spoilers (but it doesn't look like the researchers intended for that, either). I just don't think he should dismiss it out of hand without bothering to argue the other side. Is the study authoritative? No. But it does seem to hint that we may not mind spoilers as much as we think we do, and I think that's pretty interesting.