She has sweet duets with R&B legend Dr. John on "Merry Christmas, Baby" and balladeer Brian McKnight on "Have Yourself a Merry Little Christmas," and shares the stage with rapper Lil' Bow Wow (weird, but it works) on "So Emotional" and "Christmas Time." (Quick behind-the-scenes interviews from MTV's Diary punctuate the concert.) Despite her inability to resist over-the-top vocal histrionics, Aguilera's range is impressive, whether she's performing a spirited rendition of Free's 1970 hit "All Right Now" or belting out Etta James's 1961 classic "At Last," after giving the blues singer a heartfelt tribute. --Valerie J. Nelson