you actually have two parts to the AP.
The first part is the AP which you can control in pitch and roll Ie set the pitch and it will hold it and then the roll the same.
The bit that actually drives the fancy features is the flight director bit. And its actually the flight director which decides what the inputs should be to the AP.
Personally I would use it in the enroute phase but would take it out before intercept.
I have just had to many of those older types bugger off in the wrong direction or do something stupid and I really can't be bothered dealing with it just as we are intercepting. The other thing is you are invariably way out of trim when you release it when it throws a wobbly so it gives the whole airframe a huge judder as you take it out and get it back into trim.
Did 2 approaches today in 550m RVR and VV001 with an AP available but unused from 8 miles out before intercept. Part from anything else it gets your hands and feet moving in some resemblance of being coordinated.