AX is good to get the car control fundamentals down, but after a certain point if you aren't a good "sight reader" in that you can pick up a course by walking it and master it in 3 runs, it's time to move on to DEs.

I stuck with AX for 8 years and felt it was 3 years too long; never could figure out a course quickly, need repetition like you would on a track.

The $/time to seat time ratio is horrible as well.