OK, so much to say.
First of all - I loved the movie. I thought it was for the most part tight. I was vested in the characters, certainly enough to be sad when they died.
I loved the incorporation of SW-saga into the film. Tarkin was the most impressive, having had the most screen-time, but including Red and Gold Squadrons (including the ill-fated Red-5 who would be replaced by Luke Skywalker) and the character faces and voices from EpIV (including lines cut from the original film), Dr. Evazan and Baba in the market, C-3PO and R2D2 for two-seconds, and the properly aged Bail Organa days before his fateful return to Alderaan. Even Princess Leia closing the movie out, not withstanding its obvious play on my nastalgia (though my biggest outstanding question is this - why was Leia at the battle to begin with? She was supposed to be getting Obi-Wan from Tatooine, and she was on a ship that wasn't doing anything in the battle anyways.)
I loved K-2SO. he brought a mix of comedy, sarcasm, and tactical benefit (C-3PO had little tactical benefit to him). And K-2's death was possibly the saddest moment in the movie.
I loved Darth Vader's saber attack at the end. We've seen good guys take down hundreds of bad guys, but have never seen the all-powerful bad guy in his prime, wipe away a squad of good guys.
I liked that the storyline gave us a reason why firing a proton torpedo at an exhaust port would set off a chain reaction that would destroy the death star.
I will also forgive a number of inconsistencies between Rogue One and Episode IV:
1) In Episode IV, the death star is just made operational. In Rogue One, it appears as though the station is operational, but not used to its full power until Alderaan.
2) In Episode IV, Vader says to Leia that the plans were beamed aboard the Tantiv IV, when in this movie, it appears they were actually beamed aboard a Mon-Calimari vessel that happened to be holding the Tantiv IV.
I liked seeing Vader in the middle of the film, but Mustafar? really? THAT'S where he decided to hang out? It seems like he would want to stay as far away from that planet as possible.
I didn't understand the importance of Forrest Whitakers character, Saw Gerrerra. The movie could have cut him out, and saved about 20 minutes. Maybe.
I've got mixed feelings about the rebel fleet being in battle the way they were. It didn't seem much like a "spy" mission any more, and also, that battle was devastating for the rebellion, based on the numbers lost. There is certainly an implication that the fleet was never really organized until they reached the Rendevouz Point, end of ESB. The ground battle was satisfying, the space battle was ok.
I loved that the Corellian Corvette rammed the star destroyer and pushed it into another destroyer to take down the shield. I made up that move with Phage, but I'll let them take credit for it.
I missed the crawl and the John Williams score at the beginning, and was glad they had it at the end.