I really miss the "America the Beautiful" Theater in the Round. It was so well done and I always felt more patriotic upon leaving. Plus, in the summer, the air conditioning was great!
I miss the Hills Brothers Coffee House and the Red Wagon Restaurant. My grandfather was the original Food Services Manager in Disneyland, so I got to know the restaurants and cafes pretty well!
I miss being able to visit Disneyland when it's uncrowded.