The original series and the movie duology that retold it ended with a finale that was heart-rendingly bittersweet yet incredibly positive, but also had a slight note of dissatisfaction. Rebellion seeks to rectify that and just... doesn't?
From a technical standpoint, the movie is fabulous. The soundtrack is lovely, and the visuals are gorgeous. What surprised me even more was the imagery: Where I found the abstract depiction of the Witches odd and jarring in the series (and to a lesser extent also in the duology), I found it absolutely beautiful in Rebellion.
But as fantastic as it looked, it could not hide some problems with the pacing I feel this movie has. A runtime of almost two hours certainly isn't short, so I wonder if it was truly necessary to spend five minutes on a fairly silly 'magical transformation' sequence that is meant to be partially satirical. Similarly, there were two quite long fight scenes that just dragged on where nothing really mattered. IMHO the pacing is one if this movie's biggest flaws; I was never quite bored but I certainly came close occasionally.
The biggest flaw, however, is the plot, or rather its conclusion. I love the premise, I love how it is revealed, I love how it is concluded. I don't love what happens after the conclusion of the premise. Similarly, I love how all our favourite characters are there, and I love how the writers managed to unify their tragic fates with the positive premise (particularly Sayaka). I don't love what they did to Homura at the end.
All in all I find the final choice the maker's did to be a questionable one. They did not want to conclude their movie trilogy with a clichéd, super sappy, overly perfect ending. Turning clichés around is one of the most beloved and major themes of Madoka Magica, so I suppose it fits the modus operandi. But the series and duology are also so beloved because their final message is so utterly positive, and the one of Rebellion just isn't. I don't really see why.
It's a bit similar to the duology, where Beginnings ended with horrible revelations and Eternal tried to fix anything, only that there is no fourth movie to fix Rebellion's ending. Which is so weird because the movie had its perfect ending, and then threw it away for another dramatic twist that just didn't get fixed in the end.
From a theatrical standpoint, I guess this is excellent. From a personal standpoint I find this fairly unsatisfying. Still an amazing movie, though. You just might want to replace the last ten minutes with 'And then they lived happily ever after' in your head.