DxOMark has just published its findings on the quality of Nikon’s new mirrorless camera sensor, and the verdict is that Nikon did a pretty good job milking quality out of the small 1-inch sensor:
With regard to its size, this ranking is a big surprise, as the Nikon J1 sensor manages to score close to or even better than larger sensors (including 4/3 sensors).
[...] On the other hand, its low-light ISO score is a bit low: 372, which reflects the impact of the sensor size. Indeed, this score is naturally dependent on the sensor size: the bigger the sensor, the more light it captures. So even though the quality of the pixels provided by Nikon is very close to that of its main competitor, its sensor size physically limits the image quality.
If low-light shooting is your thing. then you might want to look into cameras with larger sensors. However, for everyday photography the new Nikon line perform surprisingly well given how much smaller its sensor is compared to its competitors.