Analog-X - I downloaded the demo, and it IS fully functional.

alexcoppo's directions for saving the terrain in GeoControl work the same way in the demo version.

In Bryce, to import your terrain, go to File - IMPORT OBJECT - then upload your pgm file.  It will load up as an editable terrain.  
 
I'm gonna play around with it and hoping to get some great looking terrains!  There aren't any presets with the demo.