Our visit to Siena was greatly enhanced by this apartment. It was large, airy, and very comfortable. The windows opened widely, and you could view the beautiful streets of Siena. It was full of charm - not the bland, IKEA apartments that are so often available to travelers. This apartment had character, and fit the city in which it was found. Also appreciated having a washing machine at our disposal.
The neighborhood was great - good restaurants around every corner. Oh, make sure you try the house wine everywhere - it's wonderful! Yes, the streets are hilly, but it adds to the character of the city. The apartment is located close to all of the sights you'd like to see - you just have to go up and down to get to them!
Note: if you have luggage, I'd recommend taking a bus or taxi to the house - as the ups and downs seem much exaggerated when you're pulling a suitcase and sporting a backpack!
Finally, the hosts were very accommodating and helpful. They even left some wonderful local cookies for us to try. Highly recommend this apartment and Siena!