It was a very good film, but comparisons to The Force Awakens are a bit flawed since this one is a different sort of movie. I loved that they made the pre-A New Hope Rebellion look more like the WWII OSS, dubious skulduggery and all, as opposed to the shiny good guys. And speaking of WWII, the Rebel equipment and tech all looked like a sci-fi reimagining of a mix of that and Vietnam-era American equipment, so that was good to see. Distinct enough from that of the original trilogy while retaining that iconic charm. The action scenes were fantastic, and I was pleasantly surprised by the space combat, which was one thing I disliked about The Force Awakens' action scenes (and J. J. Abrams' sci-fi movies in general, the man has a hard-on for atmospheric dogfights for whatever reason). They did a bit of a visual reference to the Castle Bravo test at the end so that was cool to see. I was concerned that they were going to waste Vader but he had a kickass scene at the very end and a narmy pun right in the middle so I consider his appearance a success. K-2SO was pretty good, his final scene was probably the most touching out of all the main casts' deaths.
I did have some criticisms though. Forest Whitaker was way too over-the-top as Saw Gerrera. I like how they did the whole "he who fights with monsters" thing with his design, him being only a couple steps removed from Darth Vader with his artificial limbs and breathing apparatus, but the acting was ridiculous. He had some crazy Lovecraftian mind-reader alien that served basically no purpose other than to have an obligatory gross-out scene in the movie, so that was kind of unnecessary. Fake Tarkin was an abomination, they should have confined him to maybe one scene if they felt like they absolutely needed to have him in it, otherwise his purpose could very easily be filled by any other Imperial officer, and it wouldn't look like Ben Mendelsohn stepped into the Polar Express for a good 4 or 5 scenes. Director Krennic was a good villain in the first couple scenes but afterwards he just kind of devolved into whining to both Tarkin and Vader, so I was kind of disappointed with him. His costume is still cool though.
Overall it's definitely worth a watch and worth your time, regardless of if you like The Force Awakens or not.