That's what I've been saying about this sensor for about a year now. These Samsung cameras are "daylight" cameras. In normal light, you can expect image quality that's every bit as good as older full-frame DSLRs. In low light, these cameras are more comparable to point-and-shoot pocket cameras. If you expect to do a lot of low-light photography, you'll want to pass on these cameras. If you mostly photograph in daylight, these Samsung cameras are excellent.
If you are considering one of these Samsung cameras, you must understand how you will be using it and decide from there if you should still buy it.
One interesting note is that Samsung squeezed a little more out of the sensor on the NX20 than the NX200 or NX210. I'm not sure exactly what accounts for this, but my guess is that the software installed on that camera is slightly different, and interprets the RAW data slightly better. In any event, the differences are small and unnoticeable.
DxOMark concludes this way: "...A very good camera; it is good value for money well specified and produces larger image files than anything directly comparable. If you are not worried about shooting in low light, then the color depth and dynamic range will see it produce very high quality images whether you're shooting portraits or landscapes."