I think for me it's just the length of the corset...if it had have extended down past the hips I think it would have looked far more interesting with those pleats coming down, and also more flattering.
Kate has a habit of wearing this sort of gown, but they tend to cut her off at the waist a bit and stunt the whole look.
But I still can't get over how stunning she looks otherwise! Her hair and make up is perfection. I so so so wish she looked like this last year.