First and most importantly: the building serves as a canvas on which to display the museum's surprisingly vast modern collection. To that end, the building is largely successful. The galleries are wide and bright and they make the art look gorgeous. In a few unfortunate cases, sun shades on the windows in the north-facing rooms distort the quality of the light and negatively impact the pieces on display. The sun shades also obscure the view of Millennium Park (and the Pritzker Garden to the south) which begs the question: why have windows at all? These are minor irritants, however. As a showcase for the art on display, the Modern Wing performs beautifully.
My surprising disappointment came from the showiness of the design of Griffin Hall. Renzo Piano draws too much attention to his design by overworking certain elements. There are too many light fixtures, too many support braces, too many handrail joints, even. There is something almost fussy about the architecture. Piano wants you to notice his work. It's an unappealing display of arrogance.
Finally, there is a lightness to the space which worries me a little. The illusion of “zero gravity” is used throughout. The “reveal” makes everything – benches, the stairs, even the walls – appear to hover an inch off the ground. The effect is immediate and profound; it gives the impression that at any moment the building is going to lift off the ground and fly away. It's lovely but how it relates to the solid permanence of the original Beaux-Arts section of the Museum remains to be seen. For now, I hope the Modern Wing can settle into itself and become as established a landmark.