We loved staying at Nathalia's place and just this evening recommended it to friends who will be visiting Santiago next fall. The apartment is compact but had what we needed.
The location is wonderful. It was just steps from many great restaurants. There is even a Starbucks in the same block. There is a mini-market directly across the street. Even though the location is very central, we had no problem with noise.
We walked to all of the sites that we wanted to see. The Metro is nearby but we never felt the need to use it.