The imagination towards the creation of experience machine truly deserves respect because it provides a new potential way for people to have experience they have never had before in reality. However, I think it is not very appropriate for human beings to plug into this machine for life and preprograming their past life experience since it may bring unpredictable negative influence in some ways.
Just as it says in the paper by Robert Nozick, this action limits us to a man-made reality. So what people can experience or feel in this manmade reality can be seriously limited, or we can say all those feelings or insights from those exprience are common and comprehensible to all human beings. It is possible for humans to explore more unknown impressions towards deeper reality, but the usage of experience machine certainly wipes out this possibility.
Moreover, usage of experience machine may weaken people’s ability to face up to difficulties in their real life. Since people can easily get their desirable feelings and impressions from simulated experience, they would lose courage and prefer to avoid all predictable suffering and pain that they need to get through in reality. There would be a lack of motivation which may block the overall development for human beings.
Actually physical feelings do not equal to mental feelings. Although the experience machine grants people an opportunity to have mental feelings from simulated experience, they will never have real physical feelings and impressions since they definitely does not do those things by themselves in reality. So the experience given by the machine is actually limited and not complete.