Just got back from Rogue One. It's a great movie. Better than TFA in my opinion, and very different too. I won't give any spoilers, because there are plenty of unexpected surprises in there for fans, but it ties in very nicely to ANH (which I rewatched earlier today), ending pretty close to where that begins. There was one particular reference that didn't seem necessary, but I still didn't mind.
The end battle is cool, a very desperate struggle with a lot of carnage. I liked all of the characters, although K2SO was my favourite, having all of the funny lines, without being silly.
I can't imagine any legitimate reason a Star Wars fan won't love this movie, unless you're some super nitpicky EU purist or something. I don't agree with any of the few major criticisms I've seen of it.