Re writing style, medical results, reading levels, etc...
From what I've seen, query vocabulary continues to be the key factor in what's returned for a search. If you search with five-syllable or six-syllable words, you'll get content written in academic style. If you use two-syllable words, you'll generally get another set of results. Both sets of results, and a whole spectrum of results in between, might be "valid", depending upon searcher expectation, common usage, and your luck of the draw.
A search for... [how can i tell if i've got a stomach bug?]
...is going to produce very different results than a query for... [gastrowidgetitis symptoms]
I posted at length about medical results back in this April 9, 2011 thread....
In the medical results, at least, I noted that Google's results for long tail vernacular or conversational queries weren't returning the same authoritative government sites that Matt was so pleased about. To a degree, the situation has since gotten better, with authoritative sites at least capturing a broader range of long tail queries, but only if writers are in the same ballpark as searchers. In general, government sites and technical experts don't use the same vocabulary that many non-technical searchers do, and these sites don't always relate to commonly searched queries.
This is true not only in medical results, but in just about every niche I've explored, including many that you might not consider technical. I think that the query vocabulary is self-selecting... it's controlled by the user... which suggests that you consider audience demographics when you pick your writer.
The writing style, the quality and uniqueness of information, and the type of site you have, will also affect the type of traffic and inbound links you're likely to get.
Did your physician writer copy anyone else's content (which could include his own, if online)?
This question brings up another situation, commonly encountered in online and offline advice of all sorts, which I think deserves mention here... and that is that there's only a limited range of common wisdom to be drawn upon, and there are only so many ways to write it up. Content farm medical articles, eg, not only cannibalize each other... they're remarkably similar to the advice distributed by my health plan. Again, this is true in many subject matter areas, not just medical.
Within this area of remarkable similarity, all those other site quality factors that are being talked about come into play. And to the degree that one man's meat is another man's poison, this is why Google is also pushing personalization.