Raise your hand if you use your Out Of Office assistant when you go on vacation (I hope your hand is raised). Keep it raised if you also check your email while you're on vacation (probably a good majority of you still have your hand raised). Here's the big question: Keep your hand raised if you respond to email while on vacation. Hand still raised? Half raised? This is a dilemma many people face when on vacation: Should you respond to your email? There's no simple answer for this, but there are many things to consider when making this decision.
To start, sometimes you don't have a choice. If it's something urgent and you don't see anybody else taking the lead on it, you may have to send out an email. Hopefully, you've left a contact person who is competent enough to take care of this for you. However, if a decision needs to be made and you're the only one to do it, even the most competent person in the world won't be able to make it for you. On the flip side, if you don't have access to your email, then obviously you won't be responding to anything.
Most of the time, you won't run into either of the above situations. You should have a choice whether to answer it or not. In my opinion, if you take the time to leave a good person as your contact, you shouldn't have to answer it. This is my preferred path when on vacation for the following main reason: Everybody knows you’re out of the office (hopefully you've communicated this to all your clients as well), so they should not be expecting an answer back from you. By answering, you open yourself up to the possibility of having to work for the rest of your vacation, as people know you are checking your email. Obviously, this defeats the purpose of your vacation.