Midtown's constant grayness problem was exacerbated by the clouds and fog present when I visited this stretch of Park. What's a nice side-effect of this is how any bright color immediately pops against the backdrop of the street. This was something I brought up a few weeks ago when I talked about 58th Street.
With all of its empty space, Park Avenue allows for some really great views of surrounding architecture. Much of it looks like what sits next door, but the angles and lines are uniquely New York.