I'm a roadie living in Northampton, MA. I did a century up to Brattleboro, VT last summer where I had been thinking of going to Keene, NH as well. I couldn't find a suitable route to do it, though -- I didn't find NH Hwy 9 to be particularly bike-friendly (narrow shoulder, high-speed limit, trucks), and I am not at all familiar with the area. I'm thinking about doing the century again this summer because it was hella fun, and I was wondering if anybody knew of any secret way to get between the Brattleboro and Keene.
(FWIW, I ended up biking back down Brattleboro Rd on the NH side of the river. I don't recall that being super pleasurable either. Maybe I should just stick to the VT side of the river around there, unless any NH people have some advice.)