Sebastian's place is warm, comfortable spacious and well located for transportation, cafes, bars, restaurants etc. We were only four people so we had lots of room without the use of caravans (as it was winter).
The ground floor 'loft' is very Berlin and might be a bit industrial for some people tastes but we liked it. There is plentiful hot water and the multiple showers and toilet facilities helped us all get ready at the same time.
If I'm going to post negatives I would say cleaning could be improved and I can't help thinking that a couple of days rent income spent at the nearest IKEA would refresh the tired collection of glasses, crockery towels etc for the coming spring/summer season.
Over all a good place though and positive visitor experience.