This is an entirely irrational prejudice, but I hate autoresponse emails. You know: "I am out of the office until X and will reply to your message when I return."
Now, I know they serve a useful purpose. I know that they're an efficient way of letting someone know that the message was received but that the person can't respond right away.
They irritate me because--irrational, remember?--they remind me that someone else is away from email and I am not. This doesn't even address the royal pain they are if you manage a discussion list and have to delete an "I am out of the office" response for every single message sent to the list.
When a person who's doing the autoresponse thing sends me a message (please do this, meet at this time, look this up--in other words, do a favor) and then I get an autoresponse in return, it's as though the person has sneaked away from the Fortress of Solitude (where I can't be, remember) to shoot an arrow and then has retreated to the fortress. The autoresponse in this case just says "I have important things to do, so would you do this task for me, since you have more time than I have?"
Well, no on both counts. And if I could, I would send you a flaming arrow of autoresponse back to your Fortress of Solitude telling you so.