Spoilers ahead, so if you haven´t seen the movie yet and don´t want to spoin it, don´t read. You have been warned!
Roguw One is an interesting experiment. Its a Star Wars movie and at the same itme it isn´t. Its not part of the episodes, which focus on the lives and times of the Skywalker family, but is playing in the same universe focusing on other people. Basically it does what Star Wars Rebels is doing and the old Extended Universe (now Legends) used to do: It gives us a broader view of the galaxy far, far away by world building. I may be a bit biased here, since I love world building! Rogue Onegives us a backstory of not only how the rebels stole the plans of the Death Star but also of the planning and constuction of the Death Star itself. It also gives us a satisfying explanation why the construction of the first one too almost 20 years but the second one was half finished (but operational) in just four years. The film was also quite brutal. It brought the war in Star Wars. Urban combat that eeriely resembles what happens in Syria, airial bombing raids, space battles and beach assaults.We see many new locations and meet new characters and familiar faces. I liked the new locations Jedah was interesting location, since it was a sacred place to those who believe in the force, kind of a Star Wars universe version of Mecca. I wished we could have seen more of the place before the Empire nuked it. We saw more of the Rebel Alliances HQ on Yavin 4 which was neat and I loved the brief glimpse at Darth Vaders very mordor-ish looking castle.. Speaking of Vader, he was used in this movie very well, brief but effective. They kind of redeemed him in this for making him a tragic, kinda pathetic character in the prequels. Here was a Vader as you want to see him, menacing, scary, almost all powerfull, even snarky! His quip when he force choked Krennic made me chuckle. I loved the brief scene at the end where he boarded the rebel ship, he smashed the rebel soldiers like an angry dark god. The characters were all quite good and sympathetic, sypathetic enough that it really saddend you when they all died. Yes, all (ALL!!!) main characters die, which is unusual for a Star Wars film (and a Disney film for that matter...). I liked the sassy droid K2SO and the warrior monk Chirrut Imwe and was down when they went down. After them the main characters fell like flies. At the end when Jyn Erso and Cassian Ando were vaporized by the Death Star blast I was actually crying a little. Oh and I loved the death of Director Krennic, the main villian of the film, it kinda felt like the Death Stars laser was aiming at him directly when he was standing on top of that tower. The effects were amazing. The CGI replicas of Grand Moff Tarkin (Peter Cushing is dead for almost 30 years) and young Princess Leia were close to perfect, only sometimes they were a little uncanny valley, there were moments, split seconds, when you though "huh, something is off here...". Also in this sense Rogue One was an experiment. A test how you can bring back actors from the dead, replace them with CGI-replicas. I think we will see much, MUCH more of this in the future.
In conclusion, watch it. Its a different kind of Star Wars movie buut still very awesome. I wouldn´t go as far as saying its the second best Star Wars after Empire Strikes Back, as some others reviewers did, but its in my top five.