don't have any opinion just saw their ads and saw they have dow future http://www.intrade.com there is also with forex and commodities http://www.enetspeculation.com Generally spread betters are not great as for fees and slippage and they can directly take position against you.
As I understand it, spreadbetting is big in the U.K. because gambling profits are not taxed. Not really a need for it in the US.