I saw the original Broadway cast twice, and the replacement cast once. The first two trips were riveting theatre, the third not so much. Like someone else mentioned, I had different opinions with each trip as to whether the priest was guilty. The first time, I was certain he was. The second, I thought Aloysius simply had an ax to grind.
Regarding the film -- I loathed it. Viola Davis was lovely, but not as strong as Adriane Lenox. Amy Adams reminded me a lot of Heather Goldenhersh, but less memorable. Hoffman was miscast. And Meryl? Oy vey. I thought she was awful. I know she's a national treasure, and has a well-earned reputation, but that role was not for her. With a better director she could have been perfect. But alas, the film adaptation is a perfect example of why some writers cannot, or rather should not direct their own pieces. All in all, the film lacks any kind of tension for me. The stakes just did not translate to film, whereas in the theatre I could not breathe.