According to Nolo.com, a simple will may be all you need if you're under the age of 50, in good health, and have no reason to be concerned about leaving estate taxes for your loved ones when you die. However, they note that you may need more than a basic will if one or more of the following applies to your situation:
You want a degree of certainty to control what happens to your property after you die
You have a special needs child or other individual that you wish to address in your estate plan
You have children from a prior marriage and would like to keep some level of peace between them and your current spouse
You feel that someone might contest your will. For example, claiming that you were not mentally competent at the time the will was written, or that the will was created under duress or by fraudulent means