I think the decision to play against costume drama really works. The '80s music cues, the lack of Costume Drama dialogue (or pretentious classical drama delivery) and an impressionistic structure that mostly works from the POV of Marie Antoinette all serve to distance the viewer from getting lost in the romance of nostalgia while at the same time keeping us from condemning her as a tool of an oppressive regime. The biggest take-away of this film is that whether Marie was good or bad didn't matter, because the arena she actually had control over had only the most tangential relationship. There's a very telling moment early on in the film when one of Marie's hangers-on gossips that Madame du Barry (Asia Argento) is political because she refuses to reign only in the boudoir.
The movie functions as an amazing bait-and-switch, because it is only in the last twenty minutes that Coppola starts pulling the rug out from under us and Antoinette. For the first three quarters of the film, it's a coming-of-age/romance that we think we're watching and that Antoinette seems to think she's living in (notice how much her life is constructed around consumption and artifice). Then her portraits start getting vandalized and you start hearing the angry crowds. And the rest is literally history. How often do we think we're living one story and it turns out we're only supporting characters in another one?
Compare this to Alex Cox's Walker, where the anachronisms and ironies feel heavily italicized, or Anthony Mann's Reign of Terror, where you can mostly feel the actor and director getting uneasy any time it moves away from its weird noir moments and back into historical drama. Coppola strikes a good balance without losing focus or falling apart, and she's assembled a game, if eclectic cast (Asia Argento! Marianne Faithfull! Rip Torn! Steve Coogan!). So yeah, I'd recommend checking it out, provided you don't prefer Serious Costume Drama. Those movies have their place, but we won't run short of them any time soon.