Michael Jackson's newest (and final) single "This Is It" began streaming on the late singer's official site and hitting radio airwaves Monday at midnight this morning. The song's release comes amid much hype and nearly four months after the music icon died on June 25 at age 50, grinding the entertainment world to a halt. An upbeat R&B track, "This Is It" features Jackson's brothers, with whom he first rose to stardom as a child decades ago, on backing vocals, which is neat. The lyr