My wife and I really enjoyed the stay at Charles' place. It was exactly what we wanted and the location was awesome. We would definitely recommend it.
Some things to consider:
1. The Apartment is on the 4th floor, so if you have children or lots of heavy luggage, this probably won't be the best fit for you.
2. There is no air conditioning, so consider that if you're going in the summer.
3. The location is incredibly central to some of the best places in Lisbon and Bairro Alto is beautiful. With that being said, there 's a lot of foot traffic and a ton of noise for most of the day, although I didn't experience the noise at night like some of the other reviews pointed out.
4. There are dudes selling weed outside the entrance to the apartment basically all day, so just keep that in mind. They're relatively harmless and generally pretty polite. You'll see them all over Lisbon, so no surprise.
If you consider the above, this is a great place to stay and awesome value for the money given the location and the apartment itself. The views are beautiful and you'll have everything you need. The bottle of wine at check-in is also a nice touch.
I would definitely recommend this place when traveling.