Thanks Bilggi for the Tip!! An AT&T rep has posted many photos captured with demo unit of Lumia 1020 camera and these are the first ones with a production unit posted by someone other than Nokia. So, it is a treat for eyes!!
Good thing is that the rep has posted pictures in many lighting conditions. He has also posted comparison pics with Lumia 900 without flash in low light. Check both the photos below.
Captured with Lumia 900:
Captured with Lumia 1020:
Now, check images with and without flash of the same scene. How much details it captures with Xenon flash.
Low light without flash:
Manual focus on display. Same scene but different focuses!!
There are many high-resolution pictures as well. Check the source link for more.