The new Broadway comedy 'Living on Love' isn't just filled with clichés -- it revels in them. This is a show that has its cake, eats it, and then rubs whipped cream all over its face...That Raquel is played by Renée Fleming -- an actual opera star, making her Broadway debut == adds a yummy twist...It's all shamelessly silly, and it works: In Joe DiPietro's play, based on Garson Kanin's 1985 'Peccadillo,' broad jokes and shameless hamming make for a guilty pleasure...Wisely, DiPietro and director Kathleen Marshall let their stars play to their strengths. Fleming lets out a few trills and, though a bit stiff at times, seems to relish the high jinks. And Sills...is hilarious as the pompous, vain Vito. The show's only misstep is an 11th-hour plot twist that's as contrived as it is sentimental. Leave that at the opera, please -- we're here for dessert.