Regretfully, I gave it a "C," and I feel like that's generous.
Movie starts off great. The "baby shower" scene is genius. Hilarious, and at the same time an appropriate and effective showcase for Barry's abilities. I loved all the humor, was surprised and delighted by Gadot's appearance (I hadn't been spoiled on that), and thought I was in for a great ride for the first hour or so. And Miller, for all their real-life issues, is undeniably a very talented and engaging actor.
But the pacing started to sag in the middle, and I started to be aware that Supergirl -- the character I personally was mainly there to see -- was going to be a later addition to the narrative than I hoped.
When she finally showed up, however, I felt like it was all worth it. Calle did everything I could have wanted with the limited screentime she had, and I thought the writing for the character was pretty solid, given that they had to basically create an arc for her out of a mere handful of scenes. She projected a strong presence and looked great in the suit. Her verbal confrontation with Zod (a welcome return by Michael Shannon) over Kal's fate was fire.
But I HATED (hated, hated, hated) the climax. So the upshot is that Kara and Keaton-Batman FAIL AND DIE, and their Earth is presumably successfully World-Engined and all of humanity wiped out by Zod. Great. That's totally the kind of triumphant ending I love in my superhero movies, Muschietti, and the fates I wanted for our splendid new Supergirl and our beloved old Batman. Preesh.
(This would have been mitigated somewhat by the original ending that was shot, in which Keaton-Bruce and Kara show up outside the courthouse after the hearing, instead of Clooney-Bruce in what was fundamentally just a gag. But as it is, we're left with the sour taste of their deaths completely intact.)
Of course, I ate up the George Reeves, Christopher Reeve, Helen Slater, and Nicolas Cage cameo appearances like a starving dog. Wonderful, delightful, magical. Made me forget for a few moments that they had just introduced an excellent new Supergirl only to callously sacrifice her to Barry's rather trite "you can't fix everything" lesson.
I did shed a single manly tear at Barry's scene with his mom in the grocery store. Effectively emotional, but not enough to justify the damage previously done.
So yeah, that "C" is definitely generous.