I like this show. It's somewhere between "House:MD" and the medical mysteries documentary on ABC in its watchability (of course, without the fictional misanthropic medical Sherlock Holmes of the 21st century, Dr. Gregory House).
Also, Mystery Diagnosis gets into the tendency of some physicians to condescend to their patients. "Depression" is probably the single most over-diagnosed illness because it can be treated with relatively inexpensive and non-toxic drugs, and because HMOs tend to financially reward physicians who choose to do this rather than actually working down a differential diagnostic tree in a patient who is troublesome, and actually treating them for what ails them. I speak as a sufferer from a rare cancer which has metastased to my liver because my physicians, even after I had had a large, rare tumor removed from my abdomen, chose to believe that something else was the matter over a period of years.
Anyway, the show is smart, well-produced, well-researched, and compassionate to its subjects. You can also learn things watching it. So can your doctor.