Wow.

I've had enjoyable shivers several times, but at first I was really puzzled to see that site: why make such a big deal out of it, any more than you'd make a big deal over feeling nice after having a cup of coffee or something? Then I followed the Reddit links and found that people were talking about it as a "head orgasm", and realized that apparently for some people it's a really strong experience, much stronger than it is for me. Fascinating.