I just watched it and loved it!
I thought Emma Watson was perfectly cast, with her beauty and her slightly miserable face, she was Meg to a T. I don't like her much and enjoyed disliking Meg too. John Brook was very sexy, in fact all the men were, which they'd have to be because otherwise you'd just stay single and suck up to Aunt March! Friedrich was lovely! 
I liked how Marmee and Jo were the same physical type, it brought the book to life, which was never believable when sainted Marmee said to grumpy Jo "ah, you're so like me".
I loved Amy, she does look twice Laurie's age when you first see them both, but she also worked as a schoolgirl. She was probably the least sympathetic character when the book was written, remember she has to have a "sickly" child to bring out the beauty in her character as I recall....but to a modern audience you can see how determined and capable she is, she's as sympathetic as Jo if not more so.
I thought Laurie was great until after he was married, I was hoping he'd stop stooping over and look more "manly" all of a sudden. I realised that he's very much a boy until then (if not after) and I really didn't get that from the book, probably because I was young myself when I read it. There's a great contrast with the girls and all their dynamism and ambition in so many different ways, but they are so restricted. Then you have this handsome, talented, wealthy boy who really could do anything but he's quite lost, perhaps because he has too much choice, perhaps it's "the Italian in him" aka cultural differences as he's fundamentally European, perhaps it's being rudderless because he's an orphan. A great contrast to the (too) many people in the March family.
I loved the costumes, it's a great challenge to make the costumes of those times look interesting, but I'm fascinated to see how they were wrong, thanks for the video! In reality they probably had three dresses each and a few grey shawls, you couldn't film it like that.
I knew the books inside out about 25 years ago and a lot of it came back, I don't think anyone who didn't know the books would have a chance of understanding the movie. It makes sense to film it assuming the audience would know the books. Then it also livens it up to jump forward and backward in time. I couldn't bear to sit through the story burning and ice skating parts long drawn out.