My trade off for realizm is simple.  The more realistic I want my scenes to look, the more simple I make them.  I've given up the idea of making photo quality images in bryce all together.  Of course that is easy to do when this is just a fun hobby. 

As of now, I use TONS of photo shop layers to achieve realism in my renders.  My images these days are a combination of different renders of the same scene using different textures, lighting, and even adding more objects. 

Instead of rendering a scene with 50 trees.  i render 10 scenes with 5 trees each along with an object mask render for each.  After that, its off to photo shop to add each set of trees in the scene with their own layers.  I'll do that with almost every object in my scenes.  This is a great way to keep tweaking a scene and add more and more stuff until I think its done, without waiting days for a render.

My forest allure picture was the first image I created with this technique.  I used about 7 different renders for the trees and foliage alone.