disadvantage: you have to use object shaders for those entities which should have self-shadows, what includes the corresponding calculations (but fortunately I made a full set for terrain 1-skin, terrain multitexture, sprites, models, grass models, trees, map-entities), not like in case of standard pssm when using stencil buffer that requires only setting the SHADOW flag.
but "sadly" it is also an advantage: you cannot get engine bugs and if your model only has to cast shadow on terrain, no need for special model shader assigned to its material.

and I use the CAST flag in the opposite way to recieve only shadows, this way you can use static lightmap on terrain while not losing e.g. shadows casted by characters on buildings. and my editor can create static terrain lightmaps (slowly as hell).

@3run: next week it should be out, just I have to do some final tests and re-tweak shadow setting all of the example maps, which is boring... and the homepage update is also boring... and uploading is also boring... I'll get very bored next week