When the A/T is engaged, never touch them! It is only when you fly with u/s A/T you realise what a boon it is. Always setting correct climb power for you, backing off power when you level, setting cruise power and maintaining it. When they are u/s, it actually becomes hazardous because you are varying between near clacker and near min buffet! You do lose continual situational awareness as you rely on it so much. Flying such a 747 back from BKK to LHR was very hard work! Are they worth it? Yes, a million times over! Takes away a very tedious task.
On approach, you can get hands on thrust levers, disconnect A/P and then do whatever your company does to the A/T. Safe, better monitoring and control of speed by the automatics, with warnings of speed discrepancy- what can be wrong with them? While they work!