I haven't had a chance to use it a ton but first impressions (as compared to the iP4) are that low light performance is improved (not as dramatic a jump as it was from the 3GS to the 4, but improved nonetheless) and I am seeing a sizable improvement in the rendering of deep reds/pinks. They used to be saturated to the point that they lost quite a bit of detail and it's not nearly as bad now.