This is the first picture I've processed with Lightroom v4.
This was taken back in late January, on a bright sunny day, from the Chimney View overlook. The lighting was as bad as it can get, midday, sunny, cloudless sky, harsh shadows, etc., etc.. The greenery in the front was completely washed out, the river bottom was in complete shade, and the cliff in the upper right was in full sun, making it a flat lifeless gray.
It was also one of the first pictures taken with my new 18-200 lens at 70mm - f11 - 1/60sec..
At that time I processed it in Lightroom 3 and wasn't happy with the results. I just couldn't get the bluish cast out of the water without it adversely affecting the rest of the picture. I tried using HDR Efex Pro to make a faux-HDR version but that made the waterfall too purple, oh bother.
The new white balance brush in LR4 did the trick, it let me tweak the white balance of just the waterfall without affecting the river. Combine that with three or four gradients and the regular set of tweaks and it's a reasonable result from a challenging picture.