I've had one cabin crew member who got upset when I slightly opened a blind to look out whilst at the same time trying to shield the light for my fellow pax but I suspect that she was a jobsworth. Most are understanding. Don't peole ask for a window seat so that they can look outside? (Its not for easy access to the loo.)
I don't see the 787 windows being a plus point as some regulation will tell the CC to override the pax's individual controls during cruise and if you like watching the world go by from your window - tough.
I seem to recall that tridents had tinted shades so that you could still look out when the sun was shining.
Iomapaseo mentions pulling the shades down to make the cabin cooler on the ground. I got on a KLM 737 at AMS during the recent warm weekend and it does make a difference.
I know that BA dims its lights for landing & take off at night - I believe that it is so that you can see better case of an evaculation (unless you have the reading light on) but it does make seeing things out of the window at night a lot easier.
It used to be that airlines wanted window blinds to be closed was so that the IFE could be seen better before the days of individual screens. I've heard it said taht one reason that Wardair did not fit IFE to its aircraft was because a lot of passengers liked their blinds open but the person who told be that liked her blind open!