For an exceptionally-lucid take on The Deal, check out John Judis’s New Republic post, “Obama Wasn’t Rolled. He Won!,” which explains:

…In the election, Obama framed the campaign in classic Democratic terms as a contest of the party of the common man against the party of the rich, while carefully targeting the new Democratic demography. And in the two months since his reelection, he carried through on the promise of the campaign by centering the fiscal cliff negotiations on ending tax cuts for the wealthy.
The bill, the American Tax Payer Relief Act, raises tax rates back to 39.6 percent for those making over $400,000; limits deductions and credits for those making over $250,000; extends unemployment insurance; expands the earned income tax credit; and gives Congress another two months to prevent sequestration. Some of my colleagues argue that he could have gotten more, but I don’t think so. The final result, approved by the House of Representatives, saves the country from another fiscal train wreck. It also positions Obama and the Democrats very well in future fights with a Republican Party that is becoming an embattled outpost for addled billionaires and white Southern revanchists. It may not happen during Obama’s second term, but the GOP may be on the way to marginalizing itself as a political party.

“An embattled outpost for addled billionaires and white southern revanchists” has to be the most apt description of today’s GOP yet written. It’s tempting to add “and their equally-unhinged political munchkins,” but that would be gilding the lily.
Judis credits President Obama with successfully achieving his central goal in the negotiations — securing a compromise which “protected consumer demand and jobs” needed to prevent imperiling the recovery. he adds,

…The very act of avoiding the fiscal cliff and the ensuing weeks of clamor or crisis will protect America’s global reputation as a “safe haven” for investors. That’s no small matter, because foreigners’ willingness to hold and invest in dollars is a major reason why interest rates have not gone up.

In addition, adds Judis, Obama and Democratic leaders maneuvered Republicans into “a position where, in order to protect tax cuts for the wealthy, they had to risk increasing taxes for everyone by letting the country go over the cliff,” which “robbed them of what has been their defining issue. They are now left with advocating spending cuts, which, as it turns out, are only popular in the abstract.”
The President did an excellent job of leveraging the bully pulpit, explains Judis. “He campaigned publicly. He framed the issues. He put the Republicans on the defensive in a way that he failed to do during much of his first term.”
Judis acknowledges that there are legitimate concerns that “about whether Obama got enough from the negotiations.” and wonders “…Could Obama have gotten an agreement on the debt ceiling or the sequester instead of postponing these battles?” But he concludes that “Obama did not have the power to force Senate and House Republicans into a last minute deal on these issues without making very unfortunate concessions on spending and taxes.”
Looking ahead, Judis adds,

…The fiscal cliff deal took tax rates out of the discussion. What’s left are spending cuts. If Obama allows the Republicans and obnoxious groups like Fix the Debt to frame the issues, he’ll be in trouble.And he did seem to fall into this trap briefly when he proposed changing the cost of living index for Social Security. But if he reminds the public that what the Republicans andBut if he reminds the public that what the Republicans and their allies want to do is cut their Medicare and Social Security, he and the Democrats should be in good shape.

As a consequence of The Deal, Judis sees the GOP being ripped apart by divisions between House and Senate Republicans, widening regional differences and even a split in conservative lobbying groups who had oppositional interests in the fiscal cliff negotiations. As Judis notes, the reverberations included this enjoyable capper for Dems:

…After the Republican leadership refused to bring a Sandy hurricane relief bill to the floor before the end of the session – effectively killing it – New York Republican Peter King called on New York and New Jersey Republicans to withhold donations to the GOP. New Jersey Governor Chris Christie blew his top at the House Republicans.

Democratic unity is going to be critical in the months ahead to hold the edge we have achieved. Says Judis “…A process of erosion is under way that will weaken the Republicans’ ability to maintain a united front against Democratic initiatives. That could happen in the debates over the sequester and debt ceiling if Obama and the Democrats make the kind of public fuss that they did over fiscal cliff.”