I got around to thinking about this, and I don't know much about programming.
In the Enhanced Client you can do something that you can't in the 2d client. Example:
You have greater heal precasted. Someone then poisons you. You can drink a cure pot, and still have the greater heal cursor up.
In 2d client if you tried this it would cancel out the spell.
So I was wondering, does this mean that this action is client side? If so, is there a way to alter it in the 2d client?