Pros:
Located in an accessible part of town, close to public transport.
Fun part of town, close to cafes, tourist attractions, shops, supermarkets, bars & restaurants.
Great view of the city of Lisbon! This was my favorite part.
Cons:
The door to the building is difficult to open, but after a few tries you'll get the hang of it. My neighbor was kind enough to help me whenever I needed it.
Loud at night. It's a party area, so I often woke up from the sounds of people yelling. Walls are very thin so if your neighbors are loud you'll hear everything. I was working remotely but if you're vacationing, it's okay. Get earplugs.
The flat gets cold in the winter. No central heating, just portable heaters. I would not recommend going during winter.
The kitchen is poorly stocked. It would be nice to have at least bottled water and salt, sugar, and spices as a nice gesture to guests. Unless you're planning to dine out every day, you'll have to do a full grocery shopping.