I've never seen a decent movie adaption of an anime/manga I've enjoyed. I am not even going to watch the Akira movie.. I just don't see how they could turn that into a serious live action movie, it was too complex.
That said, the Maria-Sama Ga Miteru movie is looking promising. I suppose it comes down onto the nature of the manga itself.
I don't think it butchers the essence of manga/anime at all. A lot of manga have shockingly bad anime adaptions and vise-versa *coughMyHimecough*, stage adaptions, etc. If fans don't like one aspect of it, they're likely not going to stop liking the other aspects.