Thank you for your time and effort to compile this very illustrative demonstration. I had similar experiences with X5 - and got totally frustrated by horizontal noise flickering at ISO800 and above. I couldn't find the way to shoot any dark shade, late sunset or after sunset scenes so finally concluded that X5 is just "daylight use only".
Did you find the way for X5R to be useful at ISO800 and ISO1600? Is there any way to avoid fixed pattern horizontal noise (I don't mind plain grain noise, as it can be manipulated in post)?