We started staying at Swan Levine house when my brother moved to Grass Valley many years ago. Although he and his family now live in Nevada City - we still choose to stay here instead of Nevada City because we've not found anything that feels as "just right" as staying with Peggy and Howard.
The b&b offers lots of room options - we like that many rooms have a second sitting area, and some rooms have two seperate sleeping areas, which was convenient when our son was younger. For longer stays we like the apartment, which has a small kitchen and fridge, so we can stay upstairs and work if we need to (free WiFi).
Location wise we love when we don't feel like driving we can walk to Main Street, to shops, cafes, restaurants, the Center for Performing Arts, etc.
Besides the house being a very comfortable and homelike b & b, it's also a small part Grass Valley history museum and a very large part art gallery. The owners are both artists, and Howard still teaches print making in the adjacent studio, but they're also quite active in the community and are a wealth of knowledge about things to see and do in the area. And, as if his being able to teach you about printmaking and the community isn't enough, his breakfasts are always hearty, plentiful and tasty, served at your leisure or around the large dining room table. The only downside of those dining room breakfasts is that the other guests are always very interesting as well, and we often find ourselves lingering for hours and hours with other guests, rather than heading out to visit the relatives we traveled to California to see :-)