from the report...
# bug 1. UV properties are not raw editable but are reported
# as RAW_TYPE_INT by RNA causing wrong conversion
# internally (bpy_rna.c line 2205)
# bug 2. raw update of UV coordinates crash blender (rna_access.c line 252)
mtfaces.foreach_set("uv", rawuvs)
# workaround:
#for i in range(int(len(faces)/4)):
# mtfaces[i].uv = uvs[i]
# bug 3. raw update of non-array property fails (rna_access.c line 2270)
mfaces.foreach_set("material_index", mats)
# workaround:
# for i in range(int(len(mfaces))):
# mfaces[i].material_index = mats[i]
# bug 4. It is not possible to add a vertex color layer using mesh API.
me.add_vertex_color()
# no workaround...