Seemed a bit pricey at first but once you get there and you see what you get, you realize the price is absolutely fair!
Martin is a great host, providing local tips and all the amenities you could wish for (bottled water in the fridge, milk for coffee, a coffee machine and filter coffee, awesome!). The place is super clean. And of course, the location is superb, less then 10 walking minutes to Potsdamer Platz.
Only down side is the parking situation, which can be tricky, but then again it's Berlin we're talking about...