We highly recommend this apartment. It was within walking distance to all the major sites. The place was spotless and well-equipped.
In addition, Joao was a fab host. We didn't have cell or email service upon our arrival in Lisbon. He waited for us for about 40 minutes at a pre-designated destination (we were late...). Then, he spent a good amount of time with us, telling us about sites and restaurants. Most useful.
As with much of Europe, there are hills and stairs. You must be up for climbing them around Lisbon, including the stairs up to the apartment. Once you get there, it's very delightful and lots of good light.