Thank god they changed the dress in Curtain Call, for some reason I hate the poofy thing, also in PCDL.
Also, I'm sure this is not a minor detail and everyone has been discussing it (I haven't read the entire first page.. sorry 
) but in (Don't) Leave Me Alone, the color of her neck-tie changes with which dancers join her. sometimes it's just black, sometimes with pink or blue or something.
EDIT: yes it's been discussed on the first page
I'll post more details here if I notice them :p