1. It only allows you to control an entire mesh with one curve, even within the same object.
2. There needs to be some way of parenting both a curve deform and an armature skeleton to the same mesh.
3. There should be a way to define what vertices of the mesh are deformed by the curve.
Right now, the only way to use the curve deforms on any model that needs more controls than just a curve, is to use hooks on the mesh, then vertex-parent the hook empties to another mesh that can't be seen, and put a curve deform on that mesh. It gets pretty complex and cluttered, and may not even work correctly.
I think the curve deforms are a good idea, but just need to be expanded a little
