I want to keep this low on spoilers, so with regards to supporting characters, I'll keep this brief. My favorite relationship is Haymitch and Katniss; I love seeing Prim's character develop; I find Joanna absolutely fascinating; and I want to be Bogs when I grow up. I still think the love triangle seems forced and irrelevant. It doesn't bring anything to the story that wouldn't be there if Katniss and Gale were always just friends; the tension over how things would work out with Katniss and Peeta would still be present, since the question is always if Katniss wants a relationship more than who she wants. But for all that, I'm happy with the ultimate resolution.
Also, points to Collins for having major characters die in every book. As much as it hurts, it's tough to take a war story seriously if all the good guys make it through to the end.
Most strongly, I'm deeply ambivalent about the long denouement that covers the time after the war. Half of me wants the book to end right after Katniss shoots (major spoiler) and the war officially ends; from a purely dramatic standpoint I think that would be best, and I always like ambiguous endings anyway.
But I also think it's important to sometimes tell stories that don't end in explosions and kisses; glory and drama. It's important for the audience to see, now and then, that the hero is left a shell of a woman who takes years to move on from what she has seen and may never forgive herself for the role she played in the war. I am glad we get to see this side of the story.
Then I think of the way Ellen Emerson White writes characters recovering from trauma (I'm thinking of Long Live the Queen and The Road Home, in particular), and I think of some of the better hurt/comfort fics I've read, and I feel cheated. Collins tells this part of Katniss's story in broad strokes; in narrative. It's jarring after being so intimately involved in Katniss's life. Even though the present tense remains, this part of the book feels like retrospect. It doesn't match.
I see why she did it this way: matching the tone and level of detail from the rest of the series, it would take an entire book to tell the last part of the story. I just don't find it entirely satisfying.
This brings me to the epilogue. In this story it's especially poignant to include a scene that takes place twenty years later, to demonstrate that Katniss and the rebels really have changed their world. And it's necessary to show at least a little of the work it took for Katniss to get there. It would be profoundly dishonest to imply that she went straight from the war to happily-ever-after.
So. I suppose I approve of the ending after all; I just had to pick it apart first.