Lovely place, fantastic views and great amenities. Castemola is a beautiful place with a really nice atmosphere.
I drove a hire car (I'm from the UK) and I found that the roads were quite difficult. I have 7 years driving experience, and I would consider myself a good driver (never had a scrape), but I was a little nervous driving the roads. My girlfriend in the passenger seat doesn't like heights, so it was an ordeal for her. It was worth it for the views and the place, however I would proceed with caution, especially if you don't trust your driving skills.
We also received some nice food recommendations from the young girl who handed us the keys. Ciccino's pizzeria is a must go!