Originally Posted by
Malifice
So much this. The spell creates a 'friendly creature that follows your orders'.
The DM determines how it interprets those orders, and if it stays friendly to you. nothing in the spell states the Simulacrum remains friendly to you, or states the simulacrum cant use initiative in determining how to carry out those orders. Nothing states the simulacrum cant come to resent the casters control over it either.
If the one cannonical example of a simulacrim (Iggwilvs simulacrum in return to Castle Greyhawk) is any guide, they most certainly can twist orders, seek to break free from their creators control, and resent their creator.