The GX1 has been reviewed by Techradar (Click here): “Image quality is an area where the Panasonic Lumix DMC-GX1 particularly impresses. Like the acclaimed Panasonic G3, the GX1 delivers a reliable, high-quality performance in most situations, while HD movies are also clean, smooth and detailed.“.
The chinese website Mobile01 (Click here) and the japanese website DC.watch (Click here) also posted a review. But the most interesting article comed via another japanese website Itmedia (Click here) compared the GX1 ISO quality with the Sony NEX-5n. Here is an example at ISO 3200: GX1 versus NEX-5n image. I have to say the GX1 does a very good job against the camera that is known to be the deliver the best image quality of all mirrorless cameras. Only at ISO 12800: GX1 image vs NEX-5n image you can see a major difference between the two. But honestly, I have to say if you shoot from ISO 100 to 1600 you will not see any visible difference. I guess the lenses here will make the difference and that’s where Micro Four Thirds has a considerable advantage.