I am sure that there are many who have had bad experiences with immigration authorities in the US or elsewhere. I want to say that I (a US citizen) have never had a bad experience, either home or abroad, including the US, Australia, or New Zealand, UK, Ireland, Japan, and many other places. I have even had two trips to Australia in the past three years where I was traveling alone with entry and exit the same day. I was never even asked any questions. In fact, the last time (in Sept 2012), the immigration officer was unusually friendly, I thought. Australia has departure control, too, and on that trip that officer was very friendly and wished me a safe trip. I replied quite sincerely "Thank you. I love this country!" at which he gave me a big smile and a wink.

I think that much depends on how we as travelers behave with these people. It is important (I think) to greet them and smile. Answer their questions politely and honestly. Remember that often the question is not important...the officer may simply be listening for an accent or for a sign that you aren't who you say you are. If the questions seem stupid or intrusive, answer them anyway without protest. Most of the time you will soon be on your way.