Experience of automated email replies

Have you had experience with automated email replies?  Have they been satisfactory or not?  Why?  Are you sure whether you can tell whether an email is an automated reply or whether it was prepared by a human agent?

Perhaps the automated emails I receive comprise of more than 90% of the total emails I receive every day. I guess it is easy for me to spot automated emails from those who were not sent by a robot, because of the format of write-up, like it was based on a template or something. Furthermore, they have these fonts and designs that were put there to attract attention.