First part of the road is quite boring as one would expect. Gets interesting at Argeles-Gazost. The French side of the Pyrenees is a good warm up until Biescas. After that, a cascade of twisties all the way to Barbastro. The road suface is good in general, brand new road from Ainsa to Alquezar.
This is a very demanding and technical route if you want to ride fast, but its a real blast!