Susan M. Dynarski (Harvard University, Kennedy School) has posted High-Income Families Benefit Most from New Education Savings Incentives on the Urban-Brookings Tax Policy Center web site.  Here is the abstract:

If funds from education savings plans are not used for schooling, the penalties more than offset the tax benefits for lower-income families; higher-income families gain even if their children do not go to college. A new breed of tax-advantaged savings vehicle has emerged for the college bound. Earnings on both the federal Coverdell Education Savings Account (ESA) and the state-level 529 savings plan are tax-free if the funds are used for postsecondary education. The advantages of these education plans rise sharply with income for several reasons. Most obviously, those with the highest marginal tax rates benefit the most from sheltering income. A less obvious advantage lies in how the accounts are penalized if withdrawals are not used for schooling. This brief explains how these new college plans work, comparing benefits between education savings and other savings vehicles.