Katharine Hepburn IS Jo. I have to agree with Robert Osborne when he said this role "fit her like a glove."
Amy and Beth were COMPLETELY miscast. Joan Bennett was 23 playing a 11/12 year old girl!!! I was quite upset. Now, maybe it was the writing but I felt that Jean Parker wasn't right for the part of Beth. She didn't seem as selfless and caring as the Beth in the book or the Beth played by Clare Danes in the 1994 adaptation.
Paul Lukas as Friedrich Bhaer wasn't a complete miscast but he often came off as a stupid, blundering idiot instead of a wise, quiet German professor.
While I sometimes felt that Laurie was wearing too much eye-liner and lipstick and Katharine Hepburn cried altogether too much or too dramatically for Jo, it was, on the whole, a good adaptation.
I prefer the Winona Ryder/1994 version but that's probably because I've grown up with it and I can't picture anyone else in the roles.