Anecdotally, I looked through the last two weeks of my browser history. Only a handful of sites 1) weren't https, and 2) didn't also have an https equivalent:

  http://fast-code.csail.mit.edu/
  http://www.projectrho.com/
  http://www.astronautix.com/
  http://mentallandscape.com/
  http://www.sheldoncomics.com/