If you are used to trimming your plane manually, you won't get much benefit from combat trim.
It's not easy mode, not even close. All it does is add a pre-programmed amount of trim for a given airspeed. It doesn't take into account whether you are turning, climbing, diving, what your throttle setting is, etc.
What it does is make the plane flyable without using the manual trims. You still have to hold the stick and pedals a little to fly straight, but not nearly as much as you have to do with combat trim off.