I get ID'd now and then and it never really bothers me. One instance really angered me though:
I was 23, and going to meet my brother and some of his friends at a local pub. I hadn't seen my brother in a year so I was looking forward to it. Got to the bar and ordered a pint and the girl asked for ID. I didn't have any on me so I was just like "Oh, I only have my student card.. will that do?" (student card has the pass logo on it so should be accepted). She wouldn't accept that so i said it was ok and I'd just have a coke. "No, you have to leave". At this point I tried to reason with her: "look, I'm 23 years old, I've just finished work and looking forward to having a drink with my brother who I haven't seen in a year". She wasn't having any of it though so I actually had to leave the pub and let my brother and his friends down their drinks before moving on to another pub.
It was absolutely humiliating, being told to leave the premises, with a valid student ID, 5 years over the age limit. I've not been back to that pub.