I got used to lots of beeping when the entire county of other school bus driver co-workers started recognizing me on my bicycle!
I got the occasional irritated honk during my commute last year (mostly in winter when I was in the right tire-track instead of the icy bike lane). I usually just stiffen in surprise and then they are past, no worries. At least I don't jerk the handlebars, that would be a dangerous reaction. It is true that they just usually don't know that you have every right to be there on the road with them. I'm wondering if honks will lessen now that I'm in a town which seems to have lots more cyclists.