The big question is does it hurt? The answer is yes and no. If we are talking about physical pain, then NO --at least nothing unbearable. At first the two molars that are cemented with the expander was a bit sore but it went away quickly. I must note here that I have a rapid palatal expander (RPE), which is only one type of many palatal expanders. I have only had the pleasure of rotating the expander once and rotating doesn't hurt at all. I have to rotate mine twice a week.
On the other hand, if we're talking about a pain that limits one's social activities, then YES. It's very hard to eat and when you do eat, food will get stick to it -- an inevitable occurrence. Speaking with this appliance is also very limiting and frustrating because it's hard to produce proper sentences. There is also a constant puddle of saliva in the back of the mouth 24/7, which impairs one's speech by a few more degrees. HOWEVER, it has started to get better and is not all that bad. Thus, it will only get better the longer I wear it (4 months to go! fighting!)
Below is a picture of my upper jaw with the palatal expander (sorry it's kind of dark).
