We stayed for 3 nights in the appartment of Arthur & Diogo. The place was very clean and cosy. We espacially liked the little patio: excellent for having breakfast outside or a drink in the evening.
Communication with Arthur, Diogo and Sara - who welcomed us at our arrival - was very smooth. They gave us lots of information and were there to answer questions.
The appartment is based on a good location as you can reach most of the intersting places by foot. Supermarket, bakery and public transport are around the corner. Although situated in a small street, it was quite noisy in the evening and at night, so we couldn't sleep with open windows.
Conclusion: nice place to stay when visiting Lisbon!