I honestly don't care if it's an R rating or not. I'm of age; I can see it if I want.
... However, I do think an R rating would be better-suited to the material. Now, I can go into why I think the movie ratings in this country are ridiculous, but that's an entirely different issue in itself.
As for box office success? Well, there's no way to tell what that will be this early in the game, hm? Although realistically, it'll only rake in a mediocre amount of money--and not just because of the R rating (Hell, I've seen 8 year old kids with their parents in R rated films!). The DVD sales will probably end up more successful.
FAME was an R rated "musical" (of sorts) and I'm pretty sure it was pretty successful. It of course also had the hit soundtrack and hit title song going for it...
Reviews/awards attention will be key to attracting a crowd outside of the normal fan base of the material.
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