I cannot really answer this honestly because I have not worked in the PR world yet. But I completed a hospitality/PR internship over the summer and seeing PR work in the real world instead of on a textbook page is something I will never forget. The challenge with PR is that most people do not know that they are being grouped into a guest characteristic. While working in the rooms division (front desk, concierge, housekeeping, etc.) of this resort I was able to determine the different types of guests that were about to approach me in the hall or at the front desk. This is an invaluable tool to have when looking at potential customers or the potential audience that your campaign or pitch will have. After speaking for a few moments with each guest I could determine what things would keep the guest happy and what would make the guest start to get agitated or have a change in mood. Being able to quickly determine this was key in getting my guests checked in happy, or keeping them happy for the remainder of the stay.
The challenge that PR practitioners face every day is making a customer angry or upset, or insulting the audience by writing a bad press release, creating a bad ad, or even putting the wrong message out with a pitch. Working with an already agitated customer who has a very narrow idea of what they need/want is also a difficult challenge to face because any wrong move could set them off and leave you with nothing. This field is always changing in new ways for practitioners and this keeps things new and fresh.