Just got back from my showing. It was the dubbed version after all (I had assumed it was subtitled since the only cast information on AMC's website was for the Japanese cast) so there was some novelty in hearing many of these characters speaking English for the first time, but it had the side effect of me not always knowing who was speaking at first if someone was off screen. This was mainly an issue with minor characters who were in the background though, nothing major.
Anyway, the movie was fun, but didn't really change the impression I had already gotten from the advertising campaign: basically nu Movie 4, down to lifting dialogue and shots directly from the manga (and with actual Law instead of proto-Law!), but nowhere near as newcomer-friendly. Heck, it even had the exact same "throw a pirate competition as cover for a Navy massacre" premise. Bullet was pretty much a peak DBZ movie villain, having little personality or substance to his character beyond his maximum power, and his ugly CG colossus literally sucked the life from the setting by turning it into a brown wasteland. But man, the eye candy! What the movie lacked in substance it more than made up in appealing to the lizard part of my brain that enjoys watching people punch each other - many of the best animators both in-house at Toei and in their orbit worked on this movie, and that extended fight scene featuring all the Supernovas minus Zoro getting wrecked by Bullet was one of the finest and most jaw-dropping I've seen in a shonen movie. All the action in the movie was great and worth seeing on the big screen, but nothing else quite reached the level of that sequence with all the dark CG crap flying everywhere in the finale.
Lots of fun Easter egg cameos both canon and non (yo Oden, get outta here Grount), and I gotta agree that Usopp got treated pretty well character-wise, better than he has in canon lately and he was pretty much the only Straw Hat to do anything of substance aside from Luffy and Zoro. He got some scattered applause towards the end, you all know which scene that was. Speaking of the theater crowd reacted pretty well to Buggy overall, plus the "suck it marine!" guy. The theater was about half full, though most of them left when the credits started and missed the stinger.
Not the best of One Piece movies as far as actual substance goes, but certainly top shelf as far as flair and spectacle went.