I really liked this show. It had many good elements of detective work - on a whole new level. It was tricky how knowing every fact, written or otherwise, could help to solve cases that seemed so unrelated to the facts themselves, but in the end felt nothing short of realistic.
The plot was a bit too repetitive at places, especially John Doe's dilemma that was more or less force-fed into every episode; he doesn't know who he is, he doesn't know why certain people are after him... Yeah, it fit the scenes a few times, but it got a bit boring by the end.
About the end of the first - and only - season I must say that it was bad. Good episode, terrible ending, because it felt more like the first half of a two-episode combo. Now we are left with too many answers hanging, not to mention one revelation that sure was shocking, but which also felt too surreal to be true.
All in all going into my favorite shows, and it's sad to see it discontinued since it has a lot of potential to move forward and expand after this first season.