We've also stayed at Bairro Alto, in both the Deluxe Junior and Chiado suites. As others have said, the location of the hotel is fabulous. In addition, we thought the service to be outstanding and the f&b to be excellent.
I was a little less enthusiastic about the decor and description of the suites we stayed in. The Deluxe Junior, while proclaiming to have a view, had a view only of a building on the other side of the narrow street. One had to open the window and stick one's head out to get a partial view. The space was pleasant enough, but something just didn't click for me, especially given the price. Chiado had a lot more character and was more traditional in decor, but it was on the second floor looking into the square, meaning noise and light in the evening. There were several design quirks in the room that were a bit annoying, and which management was aware of. The hotel's redecoration was finished shortly before the pandemic, and I don't know if I'd label it as a success, but everyone will have his/her own preferences. We also saw the Tejo suite, which was more modern in style. It did have a good view of the city looking down towards the river and bridge.
Lisbon has no shortage of boutique properties, and those mentioned earlier in the thread also seem to be good options.