This was our first stay in Lisbon so we weren't really sure of the best place to stay. We settled on alfama after a bit of research pointed out it was great for couples and I'd definitely agree with that! Really quiet quaint streets, just beware of the hills - there are lots! - although that's true of any Lisbon neighbourhood.
Joao's apartment was perfectly placed for everything we needed. The square in front of the fado museum is great for food and drinks on an evening, and it's also easy to walk to downtown or the riverside where the are an abundance of other restaurants and bars. This apartment is a great base for all the main sites too, we went everywhere on foot, apart from on quick ride on the 28 tram.
The apartment itself had everything we needed. It's pretty compact, so you have to get on with the person you're going with