I didn't take this demo pic, it's from a RAW some German user posted in a German forum in order to challenge other users to extract as much detail out of it as possible.
Here's what I came up with using "RAW converter number 1":
This is "RAW converter number 2":
Direct comparison:
Click on images for 100% views.
As you can see, it's possible to extract plenty of detail from this tiny sensor (as long as you use external RAW converters and know how to use them). Any claims that the X20 (or its sensor) don't perform are easy to disprove. However, in order to get top performance, you have to know what you are doing when shooting and processing images. This camera won't deliver stunning detail if you use it as a P&S in full Auto mode.
Personally, I like my X20, but I consider it a small X-Pro1, not a successor to the X10. Don't let the similar exterior fool you. So I shoot it like my X-Pro1, just more carefully, because it's always more demanding to shoot with a small sensor than with a large one. Small is unforgiving, small is great for becoming a better photographer, small will quickly take you to the limits of the camera, and that's where things get interesting.
It's no coincidence that my X20 vs. X10 article illustrates a practical example of pushing the X20 over its limits. I knew exactly what to look for when I got the camera (in preparation, I looked at a few early adopter images from Japan on Flickr and downloaded the RAWs), so those were literally the first images I shot. I'm no camera salesman, I don't plug new cameras like certain bloggers do, I simply put my finger right into the wound. Because to find its limits, I have to push the camera beyond them.
It's quite interesting and unusual that the X20 offers rather limited shadow headroom, but plenty of highlight headroom when you process RAWs in Lightroom. This means that in many situations, you can benefit by exposing more richly than you gut feeling would tell you is appropriate. That takes courage (and practice), and of course you need to know how salvage the highlights in Lightroom/ACR.