Note that the new Process 2012 sliders work somewhat differently from the old ones. It took me a few hours to get comfortable with them, but I find they provide much better fine control. Also, the Clarity slider seems to be about twice as powerful....
I have Martin Evening's LR4 book, and he actually states this about the Clarity slider.
I found the Shadows slider to be a major improvement. I'm redeveloping images from previous years, and what a difference - far more detail in deep shadows that I ever achieved with previous versions.