I really think folks are getting the wrong idea about this product, or I am...
Comparing UA to AU is rediculous...
AU is meant to replace the players handbook. It is an alternative ruleset complete with its own default setting. UA is a book of alternate rules meant to be implemented into a campaign to enhance the existing rules.
Similarly, it makes little sense to be outraged by this book because they just revised the core books. This is not a further revision. This is, as far as I've seen, nothing more than a set of alternate rules which can be used with the existing rules if you care to use them.
I personally think it is a great idea. I have a very small collection of D&D material, as I only purchase what I plan to use or feel is of very high caliber. I've definately got my eye on this book!