As Kevin Roose points out, this creates the hilarious possibility that the "signature" will be on every American greenback issued while he's at Treasury. Or maybe not: Geithner had to change his John Hancock for dollar-printing purposes, so maybe Lew will too.

3. He's no moderate. Unlike Geithner, a disciple of Robert Rubin and product of Clinton-era economics, Lew is more closely aligned with class-warrior image that Obama adopted during the election campaign. A staunch liberal, he started his political career canvassing for anti-war hero Eugene McCarthy in 1968 (he was 12); his adviser at Carleton College was Paul Wellstone, later an iconic liberal senator; and one of his first jobs in Washington was working for Democratic lion and former Speaker of the House Tip O'Neill.

4. But he's earned the trust of Republicans. Despite his acute partisan sensibility, he has long had a reputation for earning the trust of and working well with Republicans. People who have had to sit across the negotiating table describe him as a fierce, hard-nosed opponent, but one who listens and works hard to come to a mutually agreeable position. There were perpetual rumors throughout Obama's first term that Geithner's exit was imminent, but the question was always whether the president could get a successor confirmed.

Having been confirmed by the Senate multiple times already, Lew is one of the few candidates who should have a relatively easy run. But he may have depleted at least some of that good will in the last few weeks, when he has served as one of Obama's top lieutenants in negotiations over the fiscal cliff. The confirmation hearings could be tense, in part because of the divisive issues sure to face the next treasury secretary: A fight over the debt ceiling is already in motion; the sequester is due to occur on March 1, barring Congressional action; and spending and budgetary issues will remain a major focus for the rest of Obama's presidency. Perhaps some senator will even ask Lew about his position on the $1 trillion coin.

5. He's part of the 1 percent. Don't take his liberalism to mean that Lew is a wild-eyed socialist though. In fact, he's a former banker. In 2008, he served as chief operating officer of Citigroup Alternative Investments, a division of the Wall Street behemoth. That group was involved in controversial practices like proprietary trading, and was involved in shorting the housing market as the economy lurched toward collapse. Perhaps in keeping with his resume, Lew has rejected the view of many fellow liberals who argue that deregulation of the financial sector contributed to the crash, saying, "[I don't] personally know the extent to which deregulation drove it, but I don't believe that deregulation was the proximate cause." Expect to hear muffled howls of unhappiness from the left, which will be glad to see Geithner go but upset at Lew's positions.