The X20's new sensor delivers much better photos than the X10.
Noise and JPEG processing
Despite its advanced sensor technology, there's no getting around the fact that the sensor is small; as a result, the Fujifilm X20's photos generally look about the same as those of competing cameras from Canon and Nikon. JPEGs look okay to ISO 200, but when the noise reduction kicks in at ISO 400, artifacts become obvious.
Part of the X20's problem is that its processing algorithms seem to treat all areas equally, so there's noise in all but the most blown-out areas. That said, I still obtained a print of another ISO 800 scene with no noticeable artifacts.