What I gained out of the peer review process was an article that had grey areas filled in and statistical methods applied better. The quality of the reviewed article was much better than the quality of the submitted article. The reviewers were reading the article with an even-handed critical eye; they weren't just looking for support for their pet opinions.
There's also an aspect of criticism - criticism is expected from reviewers, but random dude A on the internet is frequently going to get something along the lines of "who are you to criticise my methods", or any request for more info declined. "Please provide more info" will work if you need to get a paper published, but won't work if you have already published your paper on scribd - where's the motivation to do rework (beyond honour of course, but scientists are human and that does not always apply)
And then there's the point that popularity doesn't equal 'correct'. Here on HN I've seen time and time again that a throwaway popular comment gets upvotes, and a well-reasoned but unpopular comment gets downvotes. Peer-reviewed articles should be about scientific rigor, not visceral feeling. Consensus of the masses is orthogonal to the needs of scientific rigor.
The main article describes very, very little in the way of quality assurance.