My opinion: Plenty of cargo room for most starship captains makes this the prefered choice by many merchants. Although the courier be equipped some solid weapons (2 proton cannons and a proton turret) its lack of shields and armor should discourage you from fighting with it. All in all, the Courier is a low-cost ship with plenty of fuel — perfect if your in the trading buisness.
Computer controled: Being equipped with a turret allows this ship to stand still and still hit you. However a laser turret does very little damage so if your ship is equipped with a few guns (turrets are even better) you can make short work out of a Courier in no time.