"She's just so happy and giggly; it is completely out of character," said a friend about Jennifer Aniston, now that she's dating John Mayer. The NY Daily News' Jo Piazza has word that it's "a certain feature of John" that's rubbing Jen the right way. Mayer's ex-lovers, like Jessica Simpson, admit he's a hard one to get over, "not because he's a great guy," says Piazza, "but because he's a great guy, if you know what we mean." Not sure. Because he's tall? (Photo: Wire Image)