Add to this the slight shift in ISO of the fixed ISO setting in P mode is highly suggestive of pixel binning.
This commentary at Dpreview forums would tend to support what I have seen this camera do to date.
In EXR Dynamic Range Priority setting the camera has the added ability of capturing and retaining highlights and shadow detail in greater strength, while adjusting the ISO settings to suit. This only leaves the user the task of changing the EV if the exposure seems to much one way or the other. While this system works quite well I'm not convinced that the wandering ISO in this mode is going to appeal to some photographers. For me I would not as a rule shoot a small sensor camera such as this at higher than ISO 800, however this sensor is a great deal quieter that its predecessor and could well be used happily up to ISO 1600.
Switching to large image size (16mp) in P mode introduces larger amount of sensor noise typical of what you would expect from a smaller sensor, although I feel its not as bad as the HS10 was. The real surprise though is how well the sensor performs at 16mp in EXR mode. It was quite a surprise to see very low levels of noise in the larger images. In fact I could happily snap away in this mode all day with little fear of there being too much noise showing in the images. The caveat here though is that you need to ride shotgun on the Ev very carefully as the camera has a habit of being 1 stop over or under exposed from scene to scene.
Suffice to say that the sensor does what it is designed to do ( how it does it is probably a moot point to the end user), and that is give high sensitivity, with good shot to shot speed and very low levels of noise.
So far I haven't found much to complain about when it comes to the sensor performance.
Follow the highlighted links to a variety of shots taken at various settings.