For starters, extending the Bush tax rates don't provide any additional stimulus -- you'd have to lower the rates from their current, Bush-era baseline to generate more stimulus. Letting them expire might have a contractionary impact, but keeping them in place won't create more stimulus.
Based on his back-of-the-envelope math, Dean Baker of the Center for Economic Policy Research told TPM that a year-long extension of the stimulus tax cuts "should lower the unemployment rate three to four tenths of a percentage point."
In November, the Economic Policy Institute calculated that the a year-long extension of unemployment benefits would generate 700,000 jobs.
"We find, using the CBO's methodology, that the $65 billion spent on unemployment insurance extensions through 2011 would support 723,000 full-time equivalent jobs," wrote Heidi Shierholz and Larry Mishel. "If this program is discontinued, then the economy will lose these jobs."
With unemployment near 10 percent, "It's not trivial, but it's an order of magnitude less than what we should be looking for," Baker said.
And it doesn't account for even known unknowns. It's quite possible that Congress will force significant cuts in discretionary spending next year. "If they do, then that could end up being a net negative," Baker added.
That makes this plan hard to see as a quiet coup for Obama.
"Who got what out of the deal is clear. The Republicans got tax cuts for the best-off two percent and lower estate taxes for the very wealthiest families, neither of which will do much if anything to create jobs," Mishel said. "President Obama won policies that will put or keep money in the pockets of the families of the unemployed and middle and low-income families, which will increase spending and create jobs."
Late update: Paul Krugman isn't quite sold.
[W]as this worth it? I'd still say no, although it's better than what I expected over the weekend. It still greatly increases the chances of the Bush tax cuts being made permanent -- especially because the front-loading of the stimulative stuff actually worsens Obama's 2012 electoral prospects.
Overall, enough sweetener has been added to diminish, but not eliminate, the bitterness of the disappointment.