Enjoyed it quite a bit. The jumping around at first is a bit disorienting (and a lot of the first act felt too dark to tell what was happening half the time), but it got better and better as it went along. Final battle scene pushed it above TFA for me. (It also made me want a new Rogue Squadron-style game badly. I feel like the makers of this movie were as big fans of the massive dogfights and capital ship brawls as Factor 5)
Vader's voice was a bit off and his lines were a tad too cheeky (though I agree that he always had a twisted and dry sense of humor in the OT, which reminds you that he's still a man, not a machine), but otherwise he lent a lot in his short appearances by reminding you just how disproportionately powerful Force users are in the series compared the "regular" guys. (Speaking of which, I bet Chirrut wished at the end that he was a real Jedi when he had to push a lever across a no man's land). Frankly, Jyn's odd inspirational speech in the Yavin IV control room felt more forced.
K-2SO was great. At first I was expecting a forced "wacky" droid or bad attempt at replicating HK-47, but I grew to really love the guy. His design helps; I love android designs that have slightly off proportions, like they're way too tall and have long ass limbs and they don't have real faces.
Also, Vader's lava castle is a reference to the original draft for Empire Strikes Back, right? I also liked that they brought back the Order of the Whills.