The default settings for the camera on XDA2 is much better than on 2i. You get much nicer looking pics if you change the settings via 'adjust' under tools when the camera is on capture mode to:
(If anyone knows where the defaults are stored, please shout up, as you lose the new settings if you have to do a soft reset)
You will find that sometimes you need to manually set the light colour (daylight, incandescent etc) rather than leave it set on auto. Changing this setting should not affect the brightness of the captured image - just the colour, but it often does. Also the quality seems to be really poor unless you choose XL for the capture size.
Under reasonable lighting conditions the above settings will produce BETTER pics than the earlier lower res camera, but this is not true in low light conditions - the new one produces very grainy (noisy) images. You can process them to remove most of this but generally it needs a better quality image processing program than you can run on the XDA.
The other big problem I have found is that the new camera finds great difficulty in working out what the exposure should be - sometimes a very ordinary scene is hopelessly overexposed. However, you can fool the camera by briefly pointing it at the sky before framing and snapping your shot.
This carry-on really should not be necessary, and someone ought to produce a software fix.