I used Specialized Armadillo's for HHH to with bontrager puncture resistant innertubes and had 0 flats. The Armadillo's had a few 1000 miles on them already and are now officialy done for.

I have some Continental ultra gatorskin ready to go on now, they are a lot lighter, less tread (not that the specialized had much to begin with) and supposedly just as puncture proof. They where a few bucks cheaper then the Specialized, too. Both are 700x25 and both about as puncture proof as you can get. Recommended psi for the Gators is 90, max is 120. The gator is available in 700x28, not sure about the armadillo.