This was my first experience with Airbnb and it was awesome.
Marion was a very nice host. She was very flexible about the Check In time. The couch was almost like a bed, it was spacious and comfortable. The place is very safe especially if you are a girl and travelling alone.
Just behind Alewife T station, there is Bertucci's restaurant (which is walkable distance (around 7 min) from Marion's place).