So far it does seem improved over the 4 by a good bit. I managed to get some good shots at Blizzcon recently, and HDR indoors helped too. One particular shot that turned out well was of the bright screens, and the dark crowd watching the Starcraft II finals.

I can't say for certain if it's improved enough for your very high end and picky tastes, but I'm happy with the upgrade

*edit* attached the unmodified JPG from the phone, with HDR. Yep, it's still pretty grainy, but some of that is also probably the fog crap in the air. (Blizzcon has this weird need to use fog machines heavily). Being that this was taken from a device I always have in my pocket to remember an amazing matchup, I'm happy with the results.