I'm surprised no one has mentioned this. I am having some dislike for the XF1 because of the exposure being inconsistent. I think the reason is perhaps most the other users take their time and if the exposure is off just compensate by locking on a different area or use the exposure control. Also perhaps I have a bad habit of pressing the button half way down and then zoom or move around. But then at other times that doesn't cause an issue. In any case this problem wasn't an issue for me at all with the X10 nor my Canon 40D; nor any of a dozen cheap point and shoot cameras I've tried. I find that even when I take the time to let off the button and re-push half way down, it can take what feels like a long time to readjust properly.
So am i expecting to much from a good IQ POS? Might I have the same issue with the Sony Rx100? I guess the best thing to do would be to try to RX100 for a while and see but that's got it's own issues.