Re: The perfect fall foliage photo.
You can change the Hue, Saturation and Luminance in ACR by clicking on the HSL/Grayscale tab which is next to the details tab where you can sharpen or reduce the noise. It gives you much greater flexibility than the RGB available in the Photoshop saturation tab. I increased the saturation for blue and probably dropped the luminance a bit. In ACR, you can change HSL for Red, Orange, Yellow, Green, Aqua, Blue, Purple and Magenta. Do your saturation work there and I agree, ignore the saturation slider on the basic page.
Once you've made all of your adjustments in Photoshop, you can always use a saturation layer or VIVEZA to oversaturate your photo!