John Kirk,
Probably the biggest problems with the stimulus are (1) I don't think the majority has been spent yet - not many of those "shovel-ready projects;" and (2) the blast of federal spending was substantially offset by the slashed state and local spending due to balanced-budget requirements.
It's a fine mess.
Sean and Jud, tax policies to drive initiatives can have double-edged consequences. For example, take tobacco taxes. Their primary intent (I guess) was to discourage smoking. However, state governments have become used to seeing those big inflows and would be unhappy if smoking and those revenues actually declined.
Having said that, I still believe a substantial increase in gas taxes would have many beneficial consequences for our country. Reduced consumption, funding for energy innovation, funding for infrastructure improvements including mass transit, all positives.