This is a good flat in a great location; it's not really touristy, which means that there are budget supermarkets and reasonably-priced places to eat in the immediate area. It's handy for the U9 at Turmstraße, which is a couple of stops from Zoologische Garten, from where you seem to be able to go almost anywhere in Berlin (a day ticket for trains, buses and trams costs €7 and you can take children with you for free). If we hadn't got the children then we probably could have walked to most of the main sights in the centre of Berlin.
The flat itself was well-appointed, with spacious bedrooms, all the kitchen appliances you could need (inc. microwave and filter coffee machine). Lina replied quickly to our messages and was there when we arrived and when we left. It's in an excellent spot close to the main road, but tucked away just up a side street so that it's nice and quiet.
The only negatives were the stairs (no lift, so four flights with a pushchair!), and the smell of cigarette smoke coming in from outside the flat - we had to wash our unworn clothes when we got home because they smelt smoky.