We visited Berlin with a group of 11 friends, and had a lovely stay at Werners place! The house is very clean and modern with a cosy kitchen to hang out. Beds are comfortable and bathrooms are spacious.
The house is next to the U-bahn, so you are in the city centre within 15 minutes. Also, free parking in the street :)
I would really recommend this place when you're considering visiting Berlin with a group!