The first 2-3 seasons were decent with the early seasons doing all the work. But the final season was a travesty and ruined me recommending the show.
Without spoilers, this is why...
The final season introduced a group that was never mentioned in the show previously that served as a "Mary Sue" with no commitment to their development to support how they achieved what they did. You could tell it was a last minute "this should work" addition with the writer's not caring enough to make it cohesive.
There was no real meaningful closure, the basic premise of the show was never addressed and the writer's made no attempt at addressing it. The character's arches ended at season three, with the final season spending most of it's time on newly introduced characters and ones you most likely will not care if they live or die.
This show will leave you upset if you watch it through and I suggest you pass unless you don't care about a journey going nowhere with no idea of how, why or where it is heading.