I just started running a chron (my third Mage chronicle), and we transitioned to Revised rules seamlessly. Overall, MAGE Revised is definitely worth the money. The clearer rules made a deep (and positive) impact on the flavor and pace of my game.
WHAT DOESN'T WORK: Some art is cartoony, and the fiction is bland compared to the First and Second Edition material -- the intro piece in particular is simply an infodump without much entertainment value.
Rules on the backgrounds of Node and Wonder and the new trait of Resonance are intriguing, but should have been clarified in the core book or wholly moved to another publication. Inclusion of such vague rules introduces confusion into the core sourcebook. In addition, some of the changes to the Sphere rules change the Sphere interaction somewhat drastically, and adding a page summarizing those changes would have been helpful to Second Edition players.
WHAT WORKS: Rules for casting are much clearer, and the new rules on foci work beautifully. Putting a new emphasis on ritual encourages players to treat magic like magic, not psi or superpowers. Merits and Flaws are a welcome addition to the core book, and they include some wonderfully creative eye-openers. The clarification of rules governing Avatar, Arete, and accumulated successes are excellent. Aside from the omissions mentioned above, the rules are well-written and clear up a number of gray areas from Second Edition.
Expanded material on the Traditions provides a nice overview of the various factions and weaknesses of each Tradition. Each Tradition receives four pages of text that present an overview of the factions, group organization and philosophy, group drawback, and the usual stereotypes of other Traditions. The stereotypes possess far less attitude than in previous editions, but this is a minor personal quibble on my part. Each Tradition includes a new faction not presented in previous materials.
There IS a long-term plot cooking in the background now. In previous incarnations of MAGE, the Ascension War offered more of a framework than a metaplot. It was a formless war in many ways, and never seemed to carry over consistently between books. The MAGE universe seems a lot less static now, and I like the new sense of direction and momentum.
MAGE Revised presents a darker look at the MAGE setting. However, it doesn't seem that different than the old mood. Contrasting a more personal street-level flavor with the epic aspects of MAGE makes the magical side of the game that much more powerful. The book contains plenty of story ideas and is not limiting in the least. I highly recommend it.