Recommended! The appartment is in a great neighborhood, quite safe and calm but also very well connected by s-bahn and u-bahn to other parts of the city. I only used it to sleep over, but it was all very nice, clean and cozy.
I didn't get to see Jan, but he was a great host nonetheless, responsive, made sure I have everything I need and gave me very clear instructions (about the keys etc.)
All in all, a perfect place to stay for a few days in Berlin!