I stayed here with a large group of people (around 20) for an event that I organised. These apartments are wonderfully spacious. The kitchen downstairs was large enough for the whole group to gather, and there are more than enough seating areas for everyone to split off into smaller groups, to just hang out, etc. Two full kitchens and a kitchenette were plenty for our needs, and the downstairs kitchen is very spacious and has lots of counter space. The beds are comfortable, and the duvets are warm (with spare blankets provided).
Only one of the bathroom doors has a lock, which is probably fine if you know everyone you're staying with well, but with a large group I'd prefer to have locking bathrooms. (This might be my only complaint about this apartment, though.) We actually made our own 'occupied' signs on hang on the bathrooms doors.
The neighbourhood is quiet, there are cafes, restaurants and a large supermarket within very easy walking distance, and it's very close to public transport. It's also easily accessible by car from the Autobahn, but you have to park your car on the street.
I would absolutely recommend this apartment (or another of Werner's listings for this building) if you have a large group of people to stay in one apartment!