The curvature "plot" was intentionally turned off for 2007 splines. The reason that it was is that we have a problem with the way that they plotted as they approached the point of inflection in that they incorrectly represent curvature by inverting back on themselves. With the edition of the density control, you can get near the same visual feedback without the plot and without the error that it produces. For our product, as well as many of our competitors, the plot line is a line that is simply plotted through the end points of each of the combs, therefore, it is an approximation.
With that said, I understand you frustration with not having it there where it once existed and we are looking into possibly getting it put back in as a checkbox option.
Regards
PS I've posted this same response over in the SW forum with images of what I'm talking about.
Mark