I saw Rogue One last night, and I have to agree with many of the comments already made. I really liked it, but have some minor quibbles.
First, since pacing has already been mentioned, I thought it was a bit too fast. There are very few moments when the pace slows even slightly to give the audience a chance to breathe.
Although I thought most of the "Easter Eggs" were well done, the cameo appearance by R2 and 3PO felt forced and out of place. Also, at the screening I attended the audience began clapping and screaming the moment they saw them, so 3POs dialogue was drowned out and I have no idea what he said.
Tarkin and Leia. If I had to guess, I'd say they were a combination of body doubles and CG faces. Quite well done, but several of Tarkin's facial expressions and eye movements didn't look convincingly natural, and the voice actor didn't quite capture Peter Cushing's voice convincingly either. And if Leia's face wasn't CG, the makeup sure made it look as if it was.
K-2SO. I thought Alan Tudyk did a wonderful job with the voice, but would have preferred that not every line of his dialogue was designed to get a laugh.
Also, yes, John Williams' absence was noticeable. The score wasn't horrible, but it rarely supported the movie the way Williams' scores do.
That being said, for the most part I thought it worked well as an addendum to the episodic Star Wars story, and look forward to seeing it again.