In general, about the location, we think it is a big value to find such a green and quiet spot right in the middle of the city! Everything was within walking distance.
We stayed 4 days with Roberto and his wife. They were very helpful and nice. They even cleaned the apartment every day. The rooms are rather large and well equipped and accompanied by Italian style breakfast. More important for us was that, even if it was hot, the rooms themselves stayed cool and the windows had proper mosquito nets.
Roberto served us fresh tomatoes and some fruits out of his garden. He gave us also a lot of tips about Bergamo and the surroundings to welcome us, and on top of that there's a lot of touristic information available in the apartment about what to do and where to eat.
You don't need to go to Milano to find interesting stuff, you can just find it around the corner! We suggest that you take their advice at heart and not only focus on the old upper town of Bergamo if you have time but also go around in the lower city and especially in the neighborhood of the apartment because the local trattoria's and osteria's are really worth it.