I wouldn't go as far as to say that this show is "great" but it certainly had its moments, and when the logic side of the story fails the human side of it saves the day. At first I wasn't totally hooked, but I got quickly attached to these characters and was curious about what will happen next even with my reservations about the logic of the story.

The writers seemed to cherry-pick the rules of the world of the story and the limit of the protagonist's abilities, what he does and what he affects, which indicates the lack of a general rule-book and that the writers seemed to abide by the rules of the show's time travelers: just wing it.

Although it should be noted that all these things does not diminish the good work the writers did with the characters and the way they developed them, there was a good human side to the story which was definetly very interesting to say the least, and the whole thing works if you think about the sci-fi part of the show as just an enivronment for these human stories to exist.

I also hated the cinematography of the show, if there was any less colour (and the spoken language wasn't english) in the show you could've easily mistaken it for a scandinavian drama (famously known for being mostly black and white with a little colour added for good measure because, y'know... people buy expensive LCD screens), but the directing wasn't bad and I quite liked their music choices, network dramas seem to always have good music supervisors based on my experience.

Personally, I think this show got saved from being just another mediocre multi-season network drama by being cancelled early on, I'm pretty sure people would've gotten sick of it if it went on and on and on... the cancellation gave it some kind of a legacy, and this way it lives on as one of those shows you always see in those "10 Shows That Got Cancelled Too Early" lists.