Although a considerable number of people have complains about vignette effect, it is a pretty useful effect to consider. Particularly when you need to accentuate a subject of a photograph, you will find this effect to be a pretty handy one.
Proper usage of vignette will make your subject’s colors to pop out nicely. If the subject is at the middle of the scene, you will be able to make the viewer to neglect the rest of the scene and focus on the subject.
However, you shouldn’t use a heavy vignette effect. Too much of black around the subject will showcase the work of an amateur. Apart from applying vignette, you can consider increasing the contrast levels of the image and try accentuating the subject; it works most of the time!