Question about happy endings? Are you disappointed if a book series you like doesn't end with one?

I read a series like that where a girl had this magic stone, yada yada yada, and at the end the stone didn't work and everything went back to normal. It was a little disappointing but it was a great ending all the same. It just depends if you want your readers smiling at the last page or reminiscing. I think either way is good though (: