Whenever I find NOS 3M diskettes, I always snap them up. Managed to get three boxes last year and of the ten disks in the box I opened, all worked.

In order of reliability from personal experience:

3M

IBM

BASF

Sony

Verbatim

Maxell

Memorex

Nashua

Fujifilm

Generic

Office Depot

(note these are for 3.5" floppies; the order doesn't change much for 5.25" but place Elephant Memory Systems between IBM and BASF)