The reason the conduit trust rarely makes sense is that it requires that the trust pay out all of the IRA distributions. If the beneficiary lives to life expectancy, which will happen 50% of the time, nothing will be left in the trust. All of the assets will be thrown into the beneficiary's estate for estate tax purposes, and will be exposed to the beneficiary's creditors, including spouses. It's almost always better to give the trustees discretion over distributions. That way, the trustees can distribute, or not distribute, whatever amount they deem appropriate from time to time.
For more on this, see my article on this subject in the March 2004 issue of BNA Tax Management's Estates, Gifts & Trusts Journal: http://www.kkwc.com/docs/AR20041209132954.pdf
In response to Leesbro63: thanks for posting the link to Jim Lange's radio show broadcasts. I'm honored to be alongside Jack Bogle. I was the guest on 44 and 76, and John Bogle was the guest on 89.