The Oakland A's began the year with a rotation of Dallas Braden, Trevor Cahill, Dana Eveland, Brett Anderson, and Josh Outman. Those five came into the season with a total of 402 Major League innings and 63 Major League starts under their belt (pretty much all by Braden and Eveland), and Oakland took a lot of heat for leaning on so much inexperience.
The five have since gone on to be worth 61 runs above replacement by park-adjusted FIP, and 3.4 runs above average by tRA.
The rotation as a whole has been right around average, benefiting from the dropping of the seasoned Eveland and the giving of innings to the young and unproven Gio Gonzalez and Vin Mazzaro. If you take the six guys who've made the most starts, they've pitched at a pace that's only a win or two worse than that of New York's rotation despite earning about one-seventh what the are paying AJ Burnett. All despite having made a total of just 35 starts prior to 2009.
Don't ever worry about experience. Worry about ability.