At its very best: As an act of compromise it could well help to prevent a recurrence of the many recent periods of partisan deadlock of American government, which have been left American politics verging on being incapable of solving the large problems our society faces. This presupposes, of course, that all actors are indeed in good faith. It is highly unlikely [according to the CBO] to do much good for unemployment; the associated extension of unemployment benefits, and one-year cut in the payroll tax are, [according to the CBO] more likely to have a useful effect on the economy.
At its worst: It is an extremely expensive, distraction from the bigger task of balancing the federal budget and reducing unemployment that will inevitably play a big role in 2012. It does nothing at all for unemployment, while continuing to undermine the credibility of the government as fiscally responsible.
Politically: It is a move that effectively blunts a great number of Republican criticisms of Mr Obama, and ought to guarantee the passage of the extremely important START treaty [which the Republicans had *insanely* looked as if they might scuttle] and perhaps the repeal of DADT. Mr Obama does not have a strong hand at the moment---but I think an infinitely worse move would have been to fail to make a compromise. In the meantime, the point could be made moot by a strong proposal for tax simplification before 2012. It is clear that the Republicans presently lack the intellectual gravitas to construct such a proposal---let us hope that Mr Obama has.