I've been lucky enough to have a Lumia 830 in my possession for a week, along with my 735.
Obviously I needed to compare the photo quality (see the photos below). Detail captured by the 830 is obviously much higher than the 735, mostly due to it's higher MP count.
I actually prefer the flower photos from the 735, the 830 has oversaturated the flower and the bokeh effect (out of focus background) is less pronounced than the 735. This might be due to the 830 adding a sharpness filter during image processing, it certainly looks like everything is slightly too sharp. The 735 doesn't appear to apply much extra sharpening of the image.
The garden landscape photo shows a much bigger difference between the two cameras. The 830 has captured much more detail, especially on the autumnal trees. The 735 provides a brighter overall picture, but the sky behind the trees is slightly over-exposed, which has caused a lot of the detail to disappear (some trees look like they have no leaves, but they are there on the 830). Again the image from the 830 appears to be slightly over-sharpened.
All photos were taken using Microsoft Camera, all settings on auto or default.
Photo 1 - Flower Macro
Lumia 830:

Lumia 735:
Photo 2 - Another Flower Macro - Different angle
Lumia 830:

Lumia 735:
Photo 3 - Garden landscape
Lumia 830:

Lumia 735
