I liked her long hair way more, although it looked far too wiggy at times. I definitely did miss Kes after her departure, everyone added something to the show for me except Harry. And she was definitely changing as a character at the end of season 3 - more serious.
Yeah, I have to wonder how her character would have developed had she stayed on the show. Though with that said, I do like her replacement, 7 of 9, much much more.