VERY late to the party... but I finally saw Rogue One.
I just loved it! THIS is how you do a prequel, IMHO. The story works just fine, it brilliantly covers up one of the major head-scratchers of the original movie (Why the hell they made the Death Star so vulnerable?), and ties in perfectly into A New Hope.
Since none of the characters are referenced in the later films, the idea that they all may die crossed my mind during the movie, but it was kinda bleak to actually see it happen. They all went down as heroes however, their sacrifice will be remembered.
The cameos were fine for me, I was afraid about all the comments about the uncanny valley but Tarkin looked fine to me. He was essential to the plot, so he had to show up quite some times, but the Darth Vader scenes were top notch. He gets only two scenes (three if we consider one where he just appears doing nothing) and both scenes are amazing.
His welcoming of "Dude second to Tarkin" (forgot the name of the villain that oversees the Death Star construction), with his silhouette shadowing him before appearing in front of him (and while the Imperial March plays beneath) is a reintroduction of the character as iconic as it can get. And when in the final fighting scene he mows down, alone against 20 or so, the entire rebel forces is so exciting that I was essentially rooting for him, the adrenaline rush comparing to the one of a moshpit during a concert. When he force-chokes someone to the ceiling and then stabs him right there with the lightsaber, that's pure sheer badassery that reminds everyone of why he's one of the best villains of the history of cinema.
And then the final scene, with Leila appearing just to take the plans and saying that they got "hope", and it's a waste of bandwith to point out that it's a call back to the title of the first movie... coupled with the knowledge that Carrie Fisher died... that was just the perfect bittersweet way to end the movie. And I said earlier, THAT's how you do ap prequel.
Ask people the major faults of the prequel trilogy - they will criticize the dialogue, parts of the plot, the CGI work and Jar Jar Binks. For me one of the major faults is that it didn't connect well into the original movies.Watch the prequel trilogy scenes between Anakin and Obi Wan, and then watch their meeting aboard the Death Star in A New Hope... for me, personally, they don't match. At all. Even the dialogue is off, "When I left you I was but the apprentice"... dude. HE left you. For dead. To burn away on the shores of a lava lake with all your limbs chopped off. They had a point of arrival, and they missed it with the prequel trilogy. Rogue One didn't.