Although SOM has a long and storied history and is an American architectural institution, their New York office really is crap.
I'm not surprised in the least that the Diamond Tower is so dull. SOM seems to stay half a step behind the curve in order to provide just enough glass, just enough sleekness, just enough of a cool finish to an interior to provide a building with a fresh, contemporary feel.
But they'll never push for anything more than is needed, never do anything new. It's corporate garbage architecture, and this new building will go down the toilet of history with 300 Madison, 383 Madison and the "Freedom Tower" in 20 years as stuff that seems purposeless in retrospect.
SOM (along with the annoyingly beinitialed RAM Stern -- I can never forgive him for the fake-Colonial Harvard Business School) is the city's most conventional, least inelegant, least imaginative firm. They've both built their names around goofy, postmodernist, conventional schlock that no piece of old New York should be sacrificed for. I don't see how these guys get work.