We had a great time in the apartment. It's very minimalistic and has the essentials for a little romantic stay. The interior is almost japanese inspired with the sliding door, which makes it a fun challenge if someone is in the bathroom while someone is cooking.
If you are a light sleeper, you might want earplugs in case heavy rain hits the plastic window above the bed at night. But it's also gives a nice feeling of the sky and reminds me of camping, so it might even lull you to sleep. The location is great. Not too infested by tourists like Barrio Alto apart from Saturdays when the famous market is right around the corner. But even then it's fine. The little street is quaint and full of nice little old ladies popping their heads out to check out the neighbours doings and hanging their laundry.
We recommend sitting at the cafe inside the park close by, enjoying quiet city bustle, birdsong and the view of the church and the harbour.