What really made this movie great is the lengths they went to to tie everything in with A New Hope. The sets and costuming hearken back to 1977, and while special effects technology has improved, the same feel of the originals was there. It was subtle, but having the old uniforms, computer interfaces, and 1970's style haircuts made it seem like the events here could have easily happened in the weeks leading up to A New Hope. There were also a few cameos of minor characters. Dr. Evazan and Ponda Baba can be glimpsed on the street in Jedha. Red and Gold Leader participate in the final battle, and they were able to use archival footage that was cut from Episode IV to seamlessly integrate them. You also see the previous Red 5 get shot down, opening up that call sign for Luke during the battle of Yavin. The final scene features Princess Leia receiving the stolen plans for the Death Star as the Tantive IV narrowly escapes.
Grand Moff Tarkin makes an appearance as he wrests control of the Death Star from Director Krennic who was in charge of the research and construction project. Basically it serves to show the constant infighting and bureaucratic wrangling that went on in the Empire. The CGI version of Peter Cushing was surprisingly good. I wouldn't say it was absolutely perfect, there were times when he seemed a little too smooth and "off". It was definitely better than the young version of Jeff Bridges from Tron Legacy, but it didn't have the benefit of being set in a virtual computer system like Tron which served to make the CGI less jarring. However, I think the film benefited from having him in there.
Mon Mothma, Jan Dodonna, R2D2 and C3P0 make appearances on Yavin IV as well. Non-CGI for them, but the actors they found do a good job of matching up with the ones from the original trilogy. Jimmy Smits reprises his role as Bail Organa, which works great since the amount of time between the prequels and Rogue One matches up well with the amount of time we have had since the prequel movies were released.
Aside from all the easter eggs and connections to A New Hope, the story was pretty solid. Think The Guns of Navarone or The Dirty Dozen, but set in the Star Wars universe. You get to see the darker side of the rebellion and see some of of the grunts in action. It's a suicide mission, but they go anyway and manage to pull it off, even though nobody makes it out alive. There has been some backlash online about some of the production team spouting off with PC nonsense, but I didn't get any sort of political agenda from the movie. If there is one PC complaint I have, it's that there should have been more aliens.
I liked the new cast and think they did a great job. Especially Alan Tudyk as K-2SO. Seriously, that droid is one of my favorite Star Wars characters. He provided some nice subtle comedic moments, and his action scenes and sacrifice at the end were well done. Great special effects during the battle at the end. I especially liked the Star Destroyer crash.
The only nitpicks I have are fairly minor. I thought the communications seemed a little too fast. It's been previously established in other sources that FTL communication in the Star Wars universe is somewhat limited and expensive. The communication between the team and HQ on Yavin IV was instaneous as was the response time when they sent the fleet to help. Also didn't like some of the character choices they made with the Imperial pilot defector. The guy had just left Imperial service within the past few weeks at most, I don't think he'd look like a long haired dirty hippie in that short of time. Maybe the Imperial military has some very lax standards when it comes to cargo pilots.