Now in its second year, and looking a lot more 'natural'.
The stream didn't work out, so we replaced it with two spouting frogs.
They aerate the water very well, and produce a very loud splashing sound, audible throughout the garden.
The Koi are doing well, as far as we can tell, though they went to ground in late summer, and didn't reappear
until I removed the pond plants in Fall. Very strange - we actually thought they had been eaten by a predator.