My friend and I stayed for 3 nights in this very centrally located apartment. If you want to be close to the nightlife and restaurants, you can't fault its location. As others have mentioned though, the climb to the 4th floor is steep and narrow so I would not recommend for those with difficulties using stairs.
The apartment itself was immaculate- very well kept and comfortable for our stay.
The Chiado lofts team were always quick to reply when I emailed questions, they even let us know of a fashion night that was on while we were there!
Although on a main road, I couldn't hear a thing from within the apartment. It is true that there is little wifi connection in the bedrooms but that didn't really bother me as the connection was great in the living room.
I would certainly recommend to anyone wanting an apartment close to the action. Great stay!