It really was incredible, especially after watching Game of Thrones and seeing how that ending turned out. Episode 8 of season 4 was briefly at the top of IMDb, and it was an amazing revelatory episode.

First half of the final season was great, but the writing in the last half felt rushed and at times cheap. It ended up being predictable, where the rest of the show was the complete opposite. They had the ability to write better, first half of that season and prior seasons proved this, but came off as if they were trying to wrap it up too quickly and finalize the loose ends :/

As I understand they intended to have 5 seasons but condensed it to 4.

I agree the last season felt rushed but overall I felt the whole course of the show was more cohesive than most series.