It's interesting reading the comments regarding the benefits of autothrottle, and it would be easy to be left with the impression that this sytem has no 'gotchas' at all.
Wrong. Very wrong.
Whilst autothrottle is indeed a marvellous addition to an automated a/c, bear in mind that all it does is set sufficient thrust to maintain/achieve a bugged airspeed. It will do that whether or not this bugged speed is appropriate for the configuration of the a/c or not. For example, in flying an approach, bugged speed is reduced to a speed appropriate for a selection of flap, but flap is not selected. The autothrottle will still give you this bugged speed even though it may now be below that of the minimum manoeuvring speed for the current (incorrect) configuration.
In other words, if the bugged speed is wrong, then effectively you're in just as dangerous a situation as if you had no autothrottle in the first place. Add to the mix that autothrottle is primarily a jet accessory, and you potentially have a situation even more tricky to recover from than if you were flying a regional turboprop.
For as long as any automated system relies on inputs and monitoring from a fundamentally unreliable and fallible human machine, then there is no perfect system. You can talk about rules, regulations, SOPs, training, monitoring, concentration and all these other good things until you are blue in the face, but the simple fact is that people make mistakes, and they always will. You will only ever reduce the likelihood it will happen, but never eliminate it.