Ever since the design tweak became known to me I was wondering why they'd give Sayaka a hairpin, but after seeing the gang like this it all makes sense: Now every magical girl in Madoka sports some manner of hair dec. And as we all know, girls are just cuter with them.
Actually Sayaka already had a hairclip, they just gave her a 'fortissimo' hairclip. I think it's much more suiting to give her a musical hairclip. I wonder why 'fortissimo' though...