Plenty of people have chewed over the costs and benefits of including vast tax cuts in the Obama stimulus bill. It's a bit crass, but one issue that I haven't seen discussed is the impact these tax cuts will have on Obama's reelection in 2012.
As Princeton political economist Larry Bartels has discovered, Democratic presidents consistently deliver more economic growth among all income classes during any four-year period. But--strangely--Bartels found that Dems don't get as much credit for this stewardship because Republican presidents consistently deliver better economic growth during election years.
This probably isn't intentional--Republicans aren't all as Machiavellian as Richard Nixon, who did actively boost the economy in time for the 1972 election--but it does indicate that the somewhat inefficient types of stimulus favored by Republicans, such as tax cuts and military procurement, provide ancillary political benefits by kicking in over a period of 3-4 years, giving the body politic a buzz just in time for election season.
Obviously, the bulk of the stimulus should go towards shoring up the middle class and laying the groundwork for green industries (and lots and lots of high speed rail). But at the point where Obama can't think of enough stimulating ways to spend a trillion dollars, he might as well include some progressive tax relief provisions that will increase consumption, help people pay off debt, and tilt the playing field in his favor around election time.