We had a great weekend in Berlin, and in Nike's appartment. The area it is located in; Friedriechain, is great. No to busy but lots of nice shops, parks, markets and restaurants & bars.
The appartment itself is very spacious, and with the six of us we had more than enough room.
Only downside was the shower; it didn't stay in one temperature, so you had to adjust temperature constantly while taking a shower. And after two people had had a shower the water turned complety cold. We had to wait for about 20 mins untill it was warm again and the next person clould shower..
I would defitinely reccomend staying at Nike's appartment!