"Time's Arrow" seems to be a TNG fan favorite with high ratings on most major film/TV database/discussion websites and a spot on the fan-assigned Time Travel Fan Collective DVD set. While indeed a well-produced episode, "Time's Arrow" ends up to be only marginally entertaining and does not stir the same ecstatic reactions within me that it seems to do for other TNG fans.
The two-parter episode begins quite amazingly: the audience is plunged into a shocking mystery within the first 5 minutes when Earth gives Picard & Data a call to investigate an archeological site in which Data's head has been found. The find naturally shocks the crew and Data, though not in the same ways. The crew is saddened at the find, almost seeing the entire situation as Data having a terminal illness, and Picard is determined to solve the mystery. However, Data is somewhat relieved at the find. Having watched his friends and colleagues age and die around him as he does not age, Data is happy that he has an end - that he is mortal and that, one day, he will become as close to human as he could ever hope. This first character-centered half of "Times Arrow" is moving, interesting, engrossing, and poignant. An android's reaction to his own death would not be so interesting as our lovable Data's and the first few events and discussions that the Enterprise crew engages into have particular meaning for those who have seen (and enjoyed, I suppose) Star Trek: Nemesis.
However, the episode's final act or two is a colossal let-down. Firstly, the episode really disappoints in the area of villains - the Devidians look even less threatening in their 19th Century human disguise than they do in their natural form. All the mystery and substance of the episode then comes to an dead-as-a-doornail end immediately after Data finds himself back in time. What started out as an interesting and character-centered mystery in "Time's Arrow" ends up campy yarn that is a little too reminiscent of the TOS episode "City On The Edge Of Forever" and not in the right ways.