Just got back from seeing this movie and I have to tell you. I really enjoyed it.
At first, I wasn't on board with these spin off movies. Because I felt there's no need for them. That's what the newly rebooted extended universe is for with their novels, comics, and video games. But then I saw the first teaser and I was fully on board. Each trailer made it much more exciting to see it. And now that I had seen it. It lived up to the hype.
Compare this to the main movies in the saga, it's definitely more grounded and a lot more darker. This one feels more like an actual war movie and the thing with the Force takes a bit in the back seat. I like all the characters in this movie and each one I want to root for to succeed in what they should do.
If I have to nitpick, I would say it does the same thing that Force Awakens did with nostalgia and nods, but not as much. Don't get me wrong, I love Force Awakens. But, Rogue One does it a lot fewer. It feels more realistic than the main movies in the saga. Like you can tell that there's a chance that most won't make it. Although, for the characters. I wish some of them were brought out a little more so I know who they are fully, but I know them enough to care. Plus, it's great to see Darth Vader in it. He's only in it for like 5 minutes of the movie, but it's great 5 minutes. You can feel his powerful presence. He's treated like a force of nature in this flick like he was in A New Hope. Which is great because that's what Vader is suppose to feel like.
Overall, it's a great tie-in to the main movies and it's worth seeing in theaters. If you're a huge Star Wars fan, don't miss this one. :)