Gavin Morrissey, advanced planning consultant to Commonwealth Financial in San Diego, notes that one excellent use for life insurance in estate planning is within a credit shelter trust; this leverages the marital exemption.
Current tax law already allows the passing of $4 million tax free to an heir (the amount increases each year till 2010). If a spouse funds a credit shelter trust with that $4 million, the surviving spouse is allowed to access it for income and maintenance, and even to draw on the principal if necessary, but since it's inside the trust, that money is growing outside the estate of the surviving spouse.