I absolutely agree that we should all practice manual flight wherever possible. However, it needs to be said that in the modern environment we should be circumspect where we do this. In the early days, if we had a low level altitude capture for example, it didn't matter too much if we overshot by a small margin. Today we can't get away with such errors. I would suggest that if we are in a metric environment such as China and Russia, we absolutely have to engage the autopilot at minimum height. This allows the PM to monitor better and reduces the threat of setting an incorrect value.
If a SID has a low level restriction, perhaps anything less than 3000ft, we should be engaging the autopilot to better manage the level off. Complex RNAV arrivals should also be flown using all automation available.
As one post rightly stated, if you are approaching an island in CAVOK or any airport for that matter, where the weather and traffic is acceptable then we should use the opportunity to practice our hand flying skill.
My point is that I agree with all the posts so far but lets not get carried away by using poor judgement to manually fly at times when prudence dictates using the automation provided.