Just finished up the show. There were a lot of things I liked about the finale, but it left me wanting more.
Spoilers: I really, really wanted a more dramatic Big Reveal. I really wanted Merlin to stand there, not as the old man but as himself, and let loose with all his power. I get why it was a much quieter moment--because it was between Merlin and Arthur, and the core of the show is their friendship. Still, not entirely satisfying. Also, unquestionably, there needed to be more time following the revelation of Merlin's powers. It's not necessarily that loose ends needed to be tied up, but I felt there should be more than just Arthur recognizing Merlin (I did love the moments between those two). I wanted Merlin to go back to Camelot after Arthur's death (which was, of course, inevitable) and be given his dues. A few moments would have done it for me.
It feels like the creators were cut a bit short and had to wrap everything up in four episodes. Too bad.