If I have any criticism of the show at all it is for a failure in the overall story arc. First - WARNING SPOILER AHEAD. I won't say who did actually commit the murder of Dr. Kimble's wife, but I will tell you who didn't and who the writers originally intended the murderer to be - Dr. Kimble's brother-in-law. The network suits - yes, they did exist and cause trouble even in the 1960's - decided that viewers would be completely turned off by the idea of a member of Kimble's family being both the culprit and also cheating on his own wife with a member of his own extended family - Dr. Kimble's wife. After four years of challenging the audience with ground-breaking stories about the civil rights movement, family violence, and small-town corruption, and the audience favorably responding to that challenge, the network executives should have had more faith.
At any rate, the first three seasons are fantastic, I'll talk just a bit about one of my favorite episodes in season one - "Home is the Hunted". In that episode Kimble returns to his hometown when he learns his father has had a heart attack. Knowing what I do about who the killer was originally intended to be makes this episode all the more powerful, especially since it is Kimble's sister and brother-in-law who take him in and hide him and who are both so sympathetic to him. Plus the confrontation between Dr. Kimble and his brother Ray in this episode is great drama.
I highly recommend the series.