There were major ups and downs to staying here, first of which is the very steep climb up hill, followed by a 4-floor climb to get to the apartment. I understand Lisbon is full of hills but this street was particularly steep so please be mindful if you have even minor mobility issues or heavy luggage. As others have mentioned, the street cannot be directly accessed by car, but you can get dropped of at the top (Largo Calhariz), bottom (Tv. Bica Grande), or mid-point (Tv. do Cabral) of the street. There is a tram that runs up and down the hill but it only stops at the bottom and top of the street.
While we did not meet Daniel, we did meet Susana who helped us check-in and gave us pointers on the area. Messages were responded to quickly and the check-in/check-out process was very smooth and flexible with the times.
The major feature of this apartment is the incredible location. On the street itself, there are great restaurants (Estrela da Bica, Os Bons Malandros, Santa Bica), a convenience store (Simerjit Singh) a few doors down and a market (Minipreco Express) at the top of the street. Additionally, it's walking distance to Time Out Market, Santa Justa Lift, Convento do Carmo, St. Roque Church, Praça do Comércio, Alfama district, Lisbon Cathedral, St. Jorge castle and many, many more attractions. The apartment is also very close to two subway lines: Cais do Sodré (green line) and Baixa-Chiado (blue line). The apartment also looks out to the river, Christ the King and April 25th bridge.
I would recommend this apartment for one to two nights, for one to two persons. The apartment is equipped with a washer, kitchen appliances, towels and a very firm bed (the iron and hair dryer were not working during my stay). The bathroom is micro and a taller person will need to keep the bathroom door open. The stand-up shower is about 1.5m x 1.5m. The apartment has very obvious signs of wear and tear but given its spectacular location it's manageable for a night or two. Once all the balcony doors are closed the street noise is not noticeable (there is a fan and heater available). There is excellent WiFi. Bring your own toiletries and a sleep mask as there are no curtains.