Speaking from personal experience -- over about six years at this point -- there are many, many web sites on the internets that 1Password's autofill works perfectly well on, and many others where it doesn't work perfectly but fails gracefully (or at least non-destructively). "Here is one site where it makes a mistake that could be catastrophic if you don't catch it" is just not a slam-dunk proof of 1Password being "poorly designed."