I recently added a new deviation to my portfolio and it taught me a valuable lesson...
"Thou shalt not render volume objects when in a hurry!". They're a real -pain- to render correctly in bryce because they handle light a different way than regular objects with textures. While this is not exactly a difficult conclusion to reach, it's still irritating to realize you're increasing the render time by 1000% just because you added a nice cloud.
I guess this frustration comes to those using regular pencils and brushes too. I've painted a few things in my life (none of the any good) and among the things I've found hardest is to paint human bodies... I guess that's my "volume-object" with a pencil