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Also, P/CF is a good alternaive since cash is a fact but earnings is an opinion.
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I don't disagree with the sentiment of what you're saying, but current earnings does a better job predicting future earnings (and cash flow, as well) than current cash flow does. Ultimately, what you're interested in as an investor is the company's future earnings and how/when those earnings will be distributed to shareholders.
The PEG ratio isn't a great ratio for a lot of reasons. I believe The Motley Fool is readable by everyone now, so I'd recommend looking at this post which does an excellent job explaining the significant shortcomings of the ratio:
http://boards.fool.com/Message.asp?mid=14354692