4) Do you guys support Hexahedron elements? When I look through the documentation for UnitCubeMesh and BoxMesh, I see no option for non-tetrahedron elements.

We support semi-structured hexahedral meshes, though not *fully* unstructured. One has to go via the ExtrudedMesh functionality to get these.

For example, to quote Henrik in a different mailing list thread,

meshbase = RectangleMesh(Nx, Ny, Lx, Ly, quadrilateral=True)
mesh = ExtrudedMesh(meshbase, Nz, Delta_z)

Or you can supply your own base quadrilateral mesh:

m = Mesh("quadmesh.msh")

mesh = ExtrudedMesh(m, ...)

For element families supported, see http://femtable.org/ to start with.

If your cells aren't perfect cuboids then some approximations are made in the quadrature calculations; if this seems to be hurting you badly then I can give further instructions.