As I had a very busy weekend of events and family get-togethers I wasn't able to post my thoughts until now.
Overall, I really liked the movie and there was a lot that it did right. The scenes with Vader made him feel incredibly imposing as they should. The movie actually felt like a true war film moreso than any other Star Wars movie, and really showed that why all the rebels have their own stories and reasons for fighting, they are all expendable and willing to give up their lives for the greater good, I really appreciated a lot of the fanservice moments (Evazan and Ponda Baba, Red 5 getting killed making way for Luke to replace him in the BoY, all of Blue Squadron being annihilated explaining why they weren't in the BoY, etc.) And I also appreciated them throwing some people of color and women into the fighter squadrons during the Battle of Scarif to show that hey, they weren't just all white guys as seen during the BoY. Also, Hammerhead Corvette! Yay!
That said, there were a few things that I didn't dig. The digitally-recreated Tarkin and Young Leia, for one, were very jarring and Uncanny valley...y. And the ending really came out of nowhere and was pretty clearly tacked on in post-production. I also felt that the new footage of Garven Dreiss and Jon Vander (Red and Gold Leader respectively) really didn't fit in the movie and was clearly a different quality. And then, there were some other minor quibbles I had - for one, where were the A-Wings? They've been retconned to being in use BBY in Rebels (although they were before then, but Rebels is official canon) and they're among my favorite ships. I would have also liked to see some other pilots, including my favorite Star Wars character Wedge, Biggs, and mothafuckin Porkins!
Also, why was everyone calling him "Governor" Tarkin? He WAS a Governor, yes, but his official position was Grand Moff - Leia was calling him "Governor" as a dig to what he was with the Republic. Also, based on the film, I think we can retcon the A New Hope exchange at the beginning of the movie to this:
Leia: I am a member of the Imperial Senate on a diplomatic mission to Alderaan!
Vader: Bitch, I just saw your ship with the Rebels not five minutes ago.
EDIT: Actually, Biggs not being there does make sense. If you go by the deleted scenes being canon, he was on Tatooine defecting from the Empire at the time of the battle.