From what I understand the Kangen water filters separates the water into alkaline and acidic components through the process of electrolysis in order to raise the pH of the water. This allegedly helps restore the pH (by raising it) inside the body, which due to modern junk food is more acidic than optimal conditions; however, I would not expect nor could I find evidence suggesting that drinking this water would actually be able to raise the pH in the body. As far as clustering goes, the pH may affect the hydrogen bond network between water molecules. There is actually a lot of work on simulating and understanding water clusters. Such as:

"Water clusters: Untangling the mysteries of the liquid, one molecule at a time." F. N. Keutsch and R. J. Saykally (2001) PNAS 98, 10533-10540

Also, you might find this article interesting:
"Do we underestimate the importance of water in cell biology?" Martin Chaplin. Nature Reviews Molecular Cell Biology 7, 861-866 (November 2006)
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