right outside my door. it's hard, but not terribly so, if you're in decent shape and ride a lot. for me, it's not an early season ride cause i'm carrying a few more pounds than i should, and really don't get as much exercise during winter as i should, so i'm basically starting over each season.
but i've never done the "over and back" or the entire loop. maybe this season. i usually just ride from my place to the top of the pass and back down, which is about 44 miles.