I'm going to put down some random thoughts on this movie here. I'm not in the mood to write an actual review.
This one was quite different from the others in the series before it. It had a dramatically different theme, and a different moral of the story. The others were mostly trying to put across the fact that beauty is more than skin deep, and so is ugliness. But this one was about counting your blessings and being happy with what you have.
Isn't it strange, and yet so very common, for all of us to want exactly what we don't have? When Shrek was a feared ogre, he complained that nobody wanted to talk to him and everybody ran off at the sight of him. That they judged him even before they knew him. And when he had great friends and a loving family, he wanted to live like an ogre and be feared.
This movie puts forth a previously mostly unseen (except a little bit in the third episode), fierce, aggressive side of Fiona. I know a lot of people are going to find this weird and/or make weird comments on this, but this side of Fiona was so much more appealing to me. It showed her as a more independent woman who knew her own mind and did exactly as she wanted to.
This movie is not the kind of thing you would expect from a sequel to the first three movies. It seems to be a slightly different genre altogether. But it has its own appeal. And it is still a must-watch for Shrek fans.