Ursula's a great host. Talking to her was very easy and she was always supportive, attentive, and very sympathetic... not to mention her excellent command of English.
Her apartment is in a very nice area of Berlin, with many stores, cafeterias, coffee shops, and the like. Public transportation helps you get to the city centre in a matter of 10 minutes. The room that she lists is large, comfortable, and plenty of light.
There's only a terribly bad point: my trip to Berlin was not long enough :( :) Seriously: I'd definitely recommend Ursula's offer to everyone who's planning on visiting Berlin.