I was very glad to stay at Bastian's place during the week I spend in Berlin.
His flat is big, light, comfy and very well decorated, the view is really pleasant as the balcony, we all felt immediately home there.
Everything was simple and well organized and we have been warmly welcomed by Bastian and his girlfriend.
The neighborhood is very pleasant, near some very trendy area, a great park and the flat is 5 minutes away from the U-bahn and S-bahn station, which is very convenient during the stay but also to arrive and leave through both airport.

I will definitely advise some friends to stay at bastion's, and will return there myself gladly.