StoneVox is a very capable voxel editor, and I working a new version that will really improve it 
http://discourse.stonehearth.net/t/introducing-the-harpy/
The Harpy made by @Hyrule_Symbol was created using only community software (StoneVox for voxel modeling, Blender for animation)… really amazing…
Yes, currently this is done via drag and drop. Just drag the file you wish to open over the programs window and let go. StoneVox will handle the rest. StoneVox however only supports reading of .qb files, and writing of .qb and .obj. It will not open .qbcl or other Qubicle formats. SV is just a tool for StoneHearth, not for anything else.
Overall StoneVox is still in it’s infancy. Qubicle is very flushed out and very professional. If you are serious about voxel modeling it’s definitely worth the money.