I love "Sweeney Todd"! It was a very difficult musical to follow when I saw it because it's 99% sung through, very little spoken dialogue and the production I saw (the revival with Patti LuPone and Michael Cerveris) had all of the actors also serving as the orchestra so everybody was on stage all the time even if their character wasn't. But I ended up leaving the theatre so impressed, it took me awhile to even article how brilliant I thought it was. The harmonies, the counterpoint to the melodies, the typical Sondheim internal rhymes...I can listen to the cast recording everyday and still find another rhyme that I am just blown away by. "And we have some shepherd's pie peppered / With actual shepherd on top! /And I've just begun / Here's the politician, so oily / It's served with a doily / Have one! / Put it on a bun / Well, you never know if it's going to run!" That whole score is like a constant process of discovery for me.
The movie I thought was a pretty good adaptation of the show. There's a debate about whether better singers would have made it better overall but I'm not so sure I'd be willing to sacrifice the acting performances of Depp and Bonham Carter and the fact that non-singers could pull off a Sondheim score when many trained singers can't do it as a testament to their drive and talent. The problem is in theatre, the blood and gore can be very abstract but in film, it's close up and realistic and, well, Burton made it very bloody and gory. Almost too much so. But I'm not sure how he could have done it without so much blood.