partly switching from stencil shadows to shadow mapping.
put a video up about it here:
I have ended up using a mixed strategy, generally using the shadow-mapping for the terrain, but stencil shadows for characters.
the stencil shadows are kind of glitchy, and were very slow for terrain, so ended up sort of semi-permanently disabled for terrain rendering;
shadows maps don't really work well for characters (low resolution + slow update rate + redraw cost = delayed pixel blobs);
stencil shadows however allowed up-to-date shadows which more precisely show object outlines, making them better suited for things that move around (like models and characters).
stencil shadows cost in terms of projecting and redrawing shadow volumes.
shadow maps cost in a different way:
the cost of redrawing the depth cube-maps every so often;
the apparent overhead of the shadow maps being used by the shaders, which can be much bigger than expected, especially regarding smaller light sources.
so, it is this funny thing:
the sun can redraw faster and use full-scene shadows;
smaller detail point-lights, if shadow-maps are enabled, are actually considerably more expensive.