One of my favorite Lightroom features is lens correction, which can correct vignetting, chromatic aberration and distortion. I find this really useful because my lenses are not pro-grade and suffer from these issues. With lens correction, my photos look like they are from more expensive lenses. :)
I used to assume that I ought to apply lens correction to all my images. However, I found out that sometimes, it's better not to use lens correction (or to choose which issues to correct for).
I recently took a portrait of my family and some family friends. I used a Tamron 17-50 VC at 17mm, which exhibits very noticeable complex distortion (the middle of the image bulges). Here's what the distortion pattern looks like:
Notice that the middle of the closet door bulges, but the top and bottom do not. This is one of the weaknesses of this otherwise great lens.
If you look at the "corrected" image, the faces of the people at the edges look more distorted (and less flattering) than those of the uncorrected image. Take a closer look at my son's face, which appears skewed in the corrected image.
So in this case, I chose not to apply the lens correction.
Fortunately, Lightroom also allows not just turning lens correction on or off completely, but also selectively applying the lens correction to correct vignetting, chromatic aberration or distortion or any combination of those issues. You can also select the degree of correction of each issue.