I find it difficult to implement a good LOD in a voxel system that have seamless transitions when you change the distance. In your movie clip, there is such a change at 19s.
Yes, it's tricky. Eric Lengyel's transvoxel algorithm is one of the best for marching cubes (http://www.terathon.com/voxels/), and Miguel Cepero's Voxel Farm seams are pretty decent http://procworld.blogspot.fr/2013/07/emancipation-from-skirt.html, though I'm not sure what technique he uses as he has dual contour voxels. I use simple skirts for now with the skirt normal adjusted to minimize transition contrast, though I've not had time to cater for certain edge cases such as the one you spotted.
The main issue with shadow maps for me is the lack of light propagation in occluded volumes, such as caves. Otherwise they're great.