i feel i am starting to make a little progress with the bryce 6.3 renderer
see notes
notes:
(only personal experience, but may be of use to others)
The Hdri feature is almost unusable due to it's demands upon the computer.
But found i can mimic the effect and get very quick renders(faster than 5.5)
by:-
making a glass dome and putting all my objects inside that.
texture the dome using spheroid mapping with whatever landscape i wish(see reflection in egg)
set the dome material properties to 100 % diffuse, 100 % metallic, 50 % transparent.
place two infinite lights outside of dome these can easily be positioned by switching to distant view. (you can see the positioning of the lighting by the reflections off the dome)
Also by rotating the dome you can choose what parts of the texture are lighting the scene.
use one light inside the dome(close to your objects) that has a linear fall off, this is useful to give ambient light and some fine control.
Watch out for a strange effect in 6.3, disabling/enabling sun shadows also
seems to affect movable light shadows rather too strongly.(by the way turning off sunlight gives a dramatic speed increase)
This set up gives a good starting point i find.
A 800 x 800 fine AA render takes less than a minute on my rather old computer
I know these renders aren't anything to boast about yet, but at least i have a starting point. At first i was very disappointed with bryce 6.3 because it seemed to be worse than 5.5 but now i am getting a real speed gain.
I would be interested in other users experience and tips.