I am a huge fan. There was a time when I could sing "New Math" all the way through. I have the DVD of him performing - rather odd because he is in Sweden (I think) and the audience seems as though they don't speak English.
I knew all these songs by heart when I was 12 or 13. Turns out my brother-in-law went to Santa Cruz and Tom Lehrer used to help out a bit with the student light opera company, if I recall the story.