I first saw this film when I was eight years old, after receiving it as a first communion present from my mother. For months I watched the movie on an almost daily basis, and it was quickly a favorite. I thought it was absolute perfection.
Now that I am a bit older.. I notice that is does have quite a few flaws. It doesn't really capture the essence of Shaw's Pygmalion, but I don't think that should really take away from the movie; they should be treated as separate entities. Some of the sets are a little, well, cramped, but consider what they had to work with, they did a pretty good job.
And then there is the dubbing issue. I recently special on MFL on AMC, and they showed "Wouldn't It Be Loverly" and "Show Me" with Audrey's voice, and though Audrey may not have the perfect melodic voice of Marni Nixon, her voice was much more "Eliza". I really do think they should have just used her voice. If you watch "Funny Face", you get a good feel for voice, which I think is beautiful in a unconventional way.
Then, there is the question of whether Julie Andrews should have played Eliza in the film version of MFL. I've gone back and forth on this issue. Now, Audrey Hepburn is my favorite actress of all time, and Julie Andrews is a close runner-up, so it really is hard to "choose". Of course Julie's voice is much better than even Marni Nixon's... but like I said before, I don't think a perfect singing voice really would suit Eliza. And as for which would play a better Eliza overall.. I really don't know. I wasn't alive to see MFL on Broadway, so I really can't compare the two. What I do know is that Audrey gave an amazing performance. Anyway, as someone else said, if Julie had played Eliza, who would have played Mary Poppins? ;)