Jo's place is in a superb location, very close to metro stations and bus stops, it is very easy to get to the city center and the neighborhood is lively and very interesting.
The room is a good size, very basic but with everything you need for your stay. The bed is super comfortable and you can barely hear the noise from the street.
Jo was very accomodating with our check in since we ended up arriving much later than expected, he even changed his plans on Friday night so he could welcome us and was very understanding. We didn't see him for the rest of the time we were there but felt very comfortable in his home.
The apartment smells like cigarette smoke, so definitely consider that if it's a big deal to you.
We had a lovely time and would definitely go back. We highly recommend Jo's place for a nice stay in Berlin.