With some 6000+ hrs on the A320, most of which is training hours, I have two comments regarding A320 A/T.
The system is very reliable and responsive, if you leave it alone and fly the aircraft smoothly it does an excelent job. In my experience, the only problem experienced manual or auto, is when the pilot concerned was over-controlling and making a real rough ride of it.
As per FCOM 3, it is recommended to use manual thrust in certain failure conditions. And from simulator experience it certainly is noticeably easier in those failure conditions.
All in all I believe the system is excellent and only surpassed in the A330 and A340.
Have a nice day