My wife, mother in law and I stayed at David's hotel for 3 days this year. We stayed upstairs in a great room, which was absolutely spotless. My mother in law stayed in the little garden cottage, also very nice. It was by far and away the best place we visited in Italy for 3 reasons:
1) The hotel is lovely - it's in excellent condition, great gardens even a nice 'Pool.
2) The food is Excellent!
3) David and his team really do work hard to look after you.
I have noticed a few mixed reviews about Cor dei Papi, and, honestly, I am disappointed at the whining!
It's not a cheap venue, no, but, you get what you pay for, in my opinion.
This is the best place we went to in Italy - I have travelled all over the world, and on this trip alone, we also visited Rome, Florence and Tuscany. 10/10 from me.