I simply arranged the trip for my mother to stay down the street from us but I visited often and have a sense of what the place is like. My biased opinion is that the location is the best in Prague - you are in a quiet residential neighboorhood but minutes from the center of the city on public transportation. And while you can take the nearby tram into town, I would suggest at least one day renting out one of the pink bikes parked nearby and creating your own route.
Specifcally reagarding Helena's place - it is much like staying at a friend's house and she is a top host. Don't expect a sterile hotel-like room or corporate apartment, but instead a home that is clean but lived in. She really brings back the spirit I believe AirBnB was founded on years ago. Thank you Helena!