Brilliant location - right in heart of Baixa and Chiado where there are many many good restaurants and some sights. 5min walk to Rossio for train and metro.
Flat is spacious, clean and felt luxurious. Apartment block safe and if you are lucky with your neighbours, I think it would be surprisingly quiet considering how central (no loud bars in immediate vicinity). Unfortunately we had loud neighbours and it did disturb us (but I'm not sure much could have been done, just a risk you take).
Check in was smooth at a local hotel 5mins away (we arrived 8pm). Don't expect the little comforts we've come to get used to from independent, personal air bnb hosts - this is a big company (they run a hotel and many Airbnbs) - E.g no coffee pods/tea, sma amount of soap/loo roll, however the flat was lovely and we would recommend.
(tip For English travellers: the kettle is in one of the cupboards - before you resort to microwaving your tea!)