Let's all take to remember the travesty of Pierce Brosnan singing in Mamma Mia!
I suggest reading Marni Nixon's memoir. She talks about how they dubbed King and I. She and Deborah Kerr worked together on creating Anna. Marni rehearsed basically with Deborah. It became seamless. She writes later this was not the case with either Woods or Hepburn. That the dubbing was sloppy. Execs misled the actors and basically wanted Marni to just sing over the film.
As many people have brought up in other threads recently, Kerr knew they were going to dub her from the very beginning and worked with Nixon to make the best combination of vocals, wheras Woods & Hepburn recorded their vocals, rehearsed to their own voices and thought they would be used in the films. Nixon's voice was added in post-production, some say without their knowledge. The work that went into KING & I really shows and it comes off very convincingly.
I think a mix is good. For example, in "One Day More" I understood why Eponine didn't belt her part live in the overlapping section, but they should recorded her belting it and have Samantha Barks sing along to it when filming.
"I saw Pavarotti play Rodolfo on stage and with his girth I thought he was about to eat the whole table at the Cafe Momus." - Dollypop
"The gods who nurse this universe think little of mortals' cares. They sit in crowds on exclusive clouds and laugh at our love affairs. I might have had a real romance if they'd given me a chance. I loved him, but he didn't love me. I wanted him, but he didn't want me. Then the gods had a spree and indulged in another whim. Now he loves me, but I don't love him." - Cole Porter
This is an excerpt from a review of the film I found by a user on Blu-Ray.com:
"Les Miserables is a fantastic film rendition of the hit Broadway musical. I've seen the live performance 3 times over the last 10 or 11 years, and there are some significant distinctions to be made between the two. The live performances tend to be sung in beautiful, operatic voices that have earned Les Mis the honor of being one of the most beloved musicals of all time. The vocals in the movie version, however, are "gruffer" and grittier, much more in line with the actual characters of the story. I prefer the emotion and intimacy of the lyrics as performed in the movie than the live stage show."
I'm not saying this how you should feel about the film personally, I'm just saying you should at least understand why the approach worked so much for the common folks (like yours truly).
I was moved by the Les Miserables film. It's a bold movie. It just keeps coming at you with raw emotion.
But when the singing is so off at certain points that it's all you can think about, it should be fixed.
"The gods who nurse this universe think little of mortals' cares. They sit in crowds on exclusive clouds and laugh at our love affairs. I might have had a real romance if they'd given me a chance. I loved him, but he didn't love me. I wanted him, but he didn't want me. Then the gods had a spree and indulged in another whim. Now he loves me, but I don't love him." - Cole Porter
I'm personally a fan of combining studio and live takes as appropriate. And, provided the double is close enough in voice to the original, I'm fully in favor of bringing back dubbing, as long as it's all above board. Better that than tweaking someone who clearly can't sing to sound like a robot. (My ulterior motive with regard to the latter is that maybe the audience will create a big enough backlash -- "why cast him/her if he/she can't sing it" -- to allow a few film musicals to once again become star-makers rather than star vehicles down the line.)