AX TO GRIND Madonna, Sarah (inset) Despite millions worth of pyrotechnics and surprise video appearances by Kanye West, Pharrell, and Britney Spears, Madonna's Sticky and Sweet tour has turned out to be neither. Insiders say that ticket sales have been unexpectedly soft. Though the tour has grossed more than $200 million to date, critics have been largely dismissive. "Has there ever been a colder pop sex symbol?" noted the Times' Jon Pareles in a review that described her "sweaty, unhappy, exhausted face" and passionless performance, and dismissed her act as "more aerobic than erotic." It's no surprise, then, that the publicity savvy pop star is taking on Republican vice-presidential candidate Sarah Palin in hopes of stirring up a little more heat.