I loved staying at Björn and Jana's place. Their flat is just incredible. I may be worth renting the room for a few days just to discover the amazing objects they have. I would namely mention : a bubble machine, a little pink pony, neon lights and last but not least, a Lady Gaga tooth brush that plays music.
The place is also perfectly located near Langstrasse, a cool street full of nice bars and clubs. It is also very close to the train station and city center.
Björn and Janja are lovely and easy-going hosts. They welcomed me by inviting me to a party, and offering some delicious chocolate.
Bottom-line: I definitely recommend going there!