Excellent! Incredibly well located, right in the heart of old Lisbon, close to anything you might need (just steps from the subway) and convenient for getting just about anywhere in Lisbon. The hosts (Hugo and his mother Idália) were a delight and gave us many thoughtful and interesting suggestions for our stay.
* As other reviews have noted, the flat is up 5 flights of stairs but your rewarded with memorable views of the city in all directions.
* We cooked most of our meals in since the kitchen was particularly well-appointed and Lisbon's markets provide a compelling set of opportunities.
* We stayed through part of the weekend (there are bars nearby) and so the flat was a bit noisy during the evening, but less so than other flats in the neighborhood likely would have been.
A hearty 5 stars!