I found strange bug, just created new terrain, and painted textures on it.. I used simple texture instead of details one (dirt_ground_c_col.bmp), then I create additional texture layer, and after that I try to paint it on terrain, here is the result:

Anyway, I'm not pretty sure, maybe this is how it should work for now, as it's still in alpha stage All in all, I loved it! Could you add zooming with mouse wheel? It would be useful