I've never met a librarian who didn't offer enthusiastic help when asked. I'm sure there are some cranky ones out there, but I can't think of a public facing job where the workers are as cheerful and helpful as librarians. It takes a certain temperament to devote your life to encouraging others to read books.
Legend has it that Nancy Pearl, the model for Archie McPhee's Librarian Action Figure, remembers the name of everyone she's met and their favorite book. A friend of mine has met her twice and that reputation held true.