I personally would not recommend power cleans. They are very dependant on exceptional form, and could be considered dangerous even under good supervision (a power clean is basically the throwing and catching of a huge amount of weight).
There are studies that support the idea that this type of ballistic training can improve explosiveness, but a number also exist that refute the idea that you have to train in this fashion to improve your explosiveness. Research indicates the results can be achieved through less dangerous exercises (squat, deadlift, etc.) Here are the references if you would like to independently research the results:
Van Oteghen, S.L. 1975 Two speeds of isokinetic exercise as related to the vertical jump performance in women. Research Quarterly 46: 78-84.
Kanehisa, H., and M. Miyashita. 1983. Specificity of velocity in strength training. European Jouranal of Physiology 52: 104-106.
Palmieri, G.A. 1983. The principles of muscle fiber recruitment during ballistic movements. National Strength and Conditioning Journal 5(5): 22-24, 63.
Wenzel, R.R., and E.M. Perfetto. 1992 The effect of speed versus non-speed training in power development. Journal of Applied Sport Science Research 6: 82-87.
In terms of results, I believe that simply attempting to move a heavy weight through a natural range of motion quickly is what needs to be done to improve velocity implied effects. It is not actually moving the weight fast that matters, but trying to do so. What this means is that toward the end of a normal set of an exercise, when you can barely do another rep, trying to lift the weight quickly will elicit the same results. Muscle fatigue will make such a movement impossible, but the fact that you are incapable is not of importance, just that you try to.
Of course there is a good bit of dispute on both sides, and I'm not saying that I'm 100 percent right, but I have never touched power cleans because I honestly believe they are dangerous. This is a decision that your coach will probably make for you, anyway. But seriously, the best way to learn how to block a 300 pound lineman is found in lining up in front of one.
