The Whitney Biennial is the most venerable, the most watched show of its kind in the United States – a major, temperature-taking survey of what's going on in contemporary art. This year, an unusually high proportion of the artists chosen for the Biennial have connections to New England, and some of them are excellent. Unfortunately, the show as a whole is a debacle: not only incoherent, but overburdened with art about art, sloppy gestures of pseudo-revolt, dreary and repetitive video art, and arcane conceptualism.