The problem with this camera isn't the camera, and it's not even the user's photographic skills (you'll be happy to hear, congusano), it's where we are with camera tech at the moment, and the blown-out-of-proportion hype that surrounded this one.
Spot on.
What irritates me the most is that for years and years they (the camera industry, and consequently the phone industry) kept telling us that the more megapixels you have, the better the image quality, and while that was true in 2-3Mpix days, once we got to 5+ Mpix it became rather.. pointless.
I hope more people look and read trough this little website:
http://6mpixel.org/en/
its an eye opener
Another thing that I gets me is the BSI crap all the phone makers are marketing so heavily... in reality one of the main reasons for the switch from FSI to BSI sensors was the fact that they didn't have to increase the sensor size in order to increase the megapixel count. There are technical limitations to how small the pixels can be on an FSI sensor, which seems to be around 1.4 microns.. anything smaller than that gets messy.
BSI allowed them to go up to 13/16, by dipping into 1.1 micron pixels.. that way they could continue their little megapixel war and keep those same tiny 1/3" sensors.
I am not saying that BSI doesn't have potential, I am just saying that its being used by the phone OEMs for a different reason. The best phone cameras out there to date are both FSI sensors, and both of them have larger than 1/3" sensors. Like you said, with the current tech available, the only way to have any meaningful image quality gains is to increase the sensor/pixel size, and to use better optics.
On the subject of "red eyes", well... Nokia solved the issue there as well, but the Xenon systems require space, and a mechanical shutter.. The capacitors required for the flash unit in the 808 are almost as thick as the whole Galaxy S4.
Until they come up with an LED that can replicate what Xenon flashes can do, flash photography on smartphones will remain useless. Expect of course on the 808, which brings me to the "blown-out-of-proportion hype" around the 920 part... for some reason they decided to use the pureview branding for this, and considering that the Symbian phone was already in use and reviewed all over the globe, won several imaging awards, etc., everyone thought that the 920 will bring similar results, which is clearly not the case.
I don't want to get into "why they haven't brought the system to WP yet" discussion again, but for anyone interested here is a good take on the subject.. it slightly differs from my own, but still.. he has couple of good points:
Why Nokia 808 had to use Symbian...
He says we will never see it on WP,.. I strongly disagree. We will see the same, or something better.. its a matter of time.