We stayed in the apartment for a total of 1 month as we needed a rest after travelling, and some time to do some work.
The apartment is very secure as it is part of a private gated block. The location at the top of the cerro means that it has the most fantastic view of the city and the bay. With the changing weather, every day offered a different view and we loved it. The apartment is well decorated, spacious and modern and is equipped with everything you could need (fast WIFI, fully equipped kitchen, hairdryer, extra linen and blankets, a good stereo, even an electric blanket!).
It is an easy 15 min walk down the hill to the flat part of the city where the shops and amenities can be found. You have to get a Collectivo taxi back up the hill, especially if you are carrying bags. This is quick, cheap and convenient. There aren't really many shops near the apartment, just corner shops and an alcohol shop selling basics.
We generally felt safe in the neighbourhood, but it is best not to display your valuables, just in case. The area was also generally quiet part from the barking dogs and occasional drunks, but you would get this throughout the city.
The owner doesn't live in Valparaiso but he has the lovely Monika close by, ready to help with any problems or give recommendations. She was excellent with us and speaks perfect English.