Is it bad to have pupil dilation?

Not always. If you are referring to having your eyes dilated with drops in the ophthalmologist's office, this is generally safe, except when you have "narrow angles." this can be determined by your eye md. If your pupil spontaneously dilates, this can be a sign of a problem in the brain (tumor, aneurysm, etc) and should be evaluated right away by an ophthalmologist.