I recently upgraded to CS5 and have noticed some amazing features. One of the newest features that I have found to be very helpful has been the Sharpen/Noise Reduction in Camera Raw 6.
The key factor under the sharpening tab is the "Masking" slider.
This now enables the artist to easily create a mask so we can sharpen parts of the image that need to be sharpened while not touching other aspects such as a
sky where we only want noise reduction.
Here are is an example of an image I recently reworked to test the difference in this feature:
You can see I have dragged the masking slider most
of the way to the right to a set point of 90.
A key feature with this is to hold down "option"
on a mac while dragging the slider.
This enables the user to only see a black and white image of the layer mask so you can fine tune what you what masked.
In this example you can see the before and after preview of the image.
The image on top has a really nice gradient of noise reduction while keeping the sharpness and detail in the bridge and buildings.
The sky on the image below is very noisy and would not look good if printed at 100%.