Much has been made of Billy Joel's plans to ditch his career as a rock & roller and age gracefully into the supposedly sanguine world of classical music. Maybe it's the right thing to do if, as it seems, he's run out of gas as a pop songwriter. Recent years have seen no new material, only box sets and reissues of his old albums. Now comes the capper, a live album from his Millennium Concert recorded at New York's Madison Square Garden on New Year's Eve. Certainly there's still some mileage left in Joel's catalog, particularly ballads like "Summer Highland Falls" and "I've Loved These Days," and, considering the nexus of the occasion and Joel's career plans, his version of "My Life." And he also turns in sharp performances of signature pieces like "Angry Young Man," "Scenes from an Italian Restaurant," and "You May Be Right." But his between-song patter may grow tiresome over repeated listenings. Joel is known to be pretty full of himself, but after hearing him rattle on about high ticket prices and his classical ambitions, you may have had your fill of him, too.