On the whole, the play is much better dramatically, and the character Susy is better drawn-- a lot of the "hits" that Audrey Hepburn takes for being melodramatic in the film role, I think wouldn't be there if the stage script had been followed more closely. What is better, and this is mainly attributable to Hepburn's influence, is, the "blind stuff." I used to work as a sign language interpreter, and I had a certificate in Deaf-blind interpreting, so i know quite a few blind people, and once even went to a National Federation of the Blind convention. Most of the things Susy does in the play, like using sugar cubes to remember phone numbers, are just stupid, and are not really things someone going to rehab after losing her sight would ever do. Learning Braille, and using it to keep track of phone numbers, and that sort of thing IS what someone would do (few people who become blind as adults ever learn to read Braille fluently, though, but using it the way Susy does in the film is totally plausible). What's more, going to rehab classes, aka, "Blind school," is something Sam's character would encourage, over inventing things on his own for Susy to do.
But more than that, it's nice that we aren't hit over the head with it. No one has a long speech about how Susy got into rehabilitation, or the whole process or physical recovery, and rehab. She goes to blind school. She does the things we see her do, like feeling the clock (I really, really want to give her a raised-bump watch, though). That's it.
I played Mike Talman in a stage production. Play and film are very similar.