Sara was very easy to plan our stay with. We did not speak with Sergio, but Sara was always prompt to answer emails or questions (even just about Lisbon) and gave many good suggestions. Meeting her for check-in was easy and she was available during our stay if we needed her. A great host!
This apartment is definitely very central, which means it is extremely loud. Luckily, when you shut the many beautiful balcony doors it does get rather quiet (at least to us it felt more quiet since we come from major cities back in the US - if you are not used to city noise this may be different). However, when you shut the doors it became very warm overnight (no A/C and only a few small fans) so we aren't sure if we'd suggest this apartment for peak-heat months or more than 2 people (sharing a bed here would be VERY warm!).
Being so close to town meant we were only seconds from bars and restaurants and about 5-10 minutes from the center of the city where many tours meet. It also means being surrounded by many tourists and locals enjoying the nightlife from dusk until dawn (bars spilling into the streets even during open hours). Even if you did not go out, you have to find your way through the boisterous crowds back to the apartment. This would be a great spot for friends looking to go out in Lisbon and who are accepting of a younger, late night crowd.
We would suggest bringing a beach towel or asking Sara for additional towels, since you only get one each, if you plan on taking the train to Cascais or another nearby beach (which you should!). There is also no bath mat, so the bathroom gets rather wet. Having an extra towel would've made a big difference! Aside from this, the apartment had everything we needed (beds, sheets, and a coffee maker) and suited our needs for a 5 day trip in Lisbon.
Have a great time on your trip!