[SPOILERS]
I watched it tonight. My initial impression was that it was really really good. Definitely the gritty battle-heavy movie I was hoping for, though it did take me about half an hour to settle into the movie, if that makes any sense. Maybe it was the adjustment of seeing new characters, but in the episode IV time setting.
Music. I thought the music was fine. The were enough callbacks to the original themes, with a few memorable moments of new stuff as well. The part with Galen and his scientists on the landing platform was particularly moving. Only a couple of times I heard something that made me think that "John Williams would definitely not have written it this way".
Characters. I liked most of the characters, and by the end I found myself caring about what was happening to them, which I suppose it a good yardstick to judge by. I was worried that K2-SO would be the "joke robot", but thankfully his one-liners were restrained for the most part, and he ended up being pretty useful. (My pet peeve is movies that insert too much comic relief for the sake of it). For now, I'll only say that I wish we got more background on Saw Gerrera. How did he split from the rest of the Rebellion, and what was his relationship with the other rebel leaders? Jyn says that he raised her - I wish we could have had a bit of a flashback or something there to make a bit more of a connection when she's reunited with him again to get the Rebel Alliance their re-introduction. Ben Mendelsohn was great as Director Krennic. I also liked the fact that they didn't go for a straight out romance sub plot between Jyn and Cassian - there were hints towards the end, enough to make you think "what if..", and I was totally fine with that.
CG Characters. Tarkin was well done, but they just didn't have that final magic to make you believe he was real. Soo close at some points, but as soon as he was onscreen my 9 year old points to the screen and says "Dad, is he animated, is he animated?", so they didn't quite fool him either. Leia was so close, up until the point where she spoke and then it kinda gave the game away. Still, these are nitpicks, and not enough to spoil my enjoyment.
Cameos. Won't mention the other obvious one, but did anyone notice the guy from the cantina in Episode VI. The "I have the death sentence on 12 systems" guy?
Vader. Not sure if anyone else though this, but the first scene in Vader's temple with Krennic just felt a bit off. I can't even put my finger on it - not sure if it was the dialog, the physical movements of Vader, or what, but something just didn't click for me.
The part near the end with Vader vs the rebels trapped in the corridor was pure magic, and what I was itching to see as soon as this movie was announced. Worth the price of admission on its own.
Battle scenes. Definitely the best I have seen in any SW movie. Frenetic, brutal, and action packed. This must be the highest body count we've ever had in SW.
General pacing. At the start I felt like the movie was going a little slow, but the second half just kept picking up pace, and the final half hour or so was just so intense. Excellent stuff.
I don't generally like ranking stuff, and I definitely want to see it again over the next few weeks, but I think that when the dust settles, I will end up ranking this above TFA.