If each state chose its electors by CD instead of having winner take all, it would improve the system a great deal. The reason is that candidates would have to visit more states. The direction in which we are headed is very bad, we could get closer and closer to the point in time where one party has a lock on the electoral college (probably the Republicans). Not that a CD system would be all that great, it would just be a step in the right direction and could be enacted without the lengthly process of amending the Constitution.
A CD system would be a step in the wrong direction. It would cause gerrymandering to be that much more harmful, and would give state legislatures a huge amount of leverage in determining how their state's EVs will be cast.