Some interesting comments, my thoughts are that shutting the engine down should be part of training provided it is done by an approved person [instructor etc]. It is a very different experience the first time "the fan" stops for real or by choice.
My first engine failure happened on my first flight in my own plane after getting my license and although I didn't think so at the time, looking back now it was probably the best thing that could have happened. I learnt more in the next 30 seconds than I had learnt in the previous 20 hours. I have to say that I nearly didn't fly again but it has made me very cautious about flying anywhere where there isn't somewhere to go if things go quiet.
I practice engine outs on a regular basis and providing you are sensible it is quite safe. I wouldn't do it on a public aerodrome as it is illeagle to do it but it gives me peace of mind that I know my plane and I also know that I can handle the situation if it crops up. In my opinion if you know you can land the plane without the motor, you will be less stressed and less likely to make a stupid decision that might result in damage to the plane and more importantly the pilot when the situation arises. Engine failures ,while they are not that common an occurence, should be viewed as an inevatable factor in flying not a 'one day it might happen'. The longer you go without one, the closer you are getting to one so "be prepared" is my motto.
Regards Mark