The jury is still out on whether or not court mandated Victim Impact Panels modify behaviors of those convicted of a DUI/DWI. Some research shows that the rate of recidivism is lower in places that require attendance of a Victim Impact Panel, while other research is not so clear. Depending on the evidence and the circumstances it may be to your benefit to attend a Victim Impact Panel prior to being ordered to do so. This ABC News article covers a brief history of Victim Impact Panels and some of the research related to their effectiveness:
http://abcnews.go.com/Health/story?id=117908&page=1
Remember, if you are arrested for a DWI, an experienced DWI attorney can help you navigate the process and advocate for you.