In 2009, he'd worked from memory and flubbed the wording, requiring a private do-over the next day.
This time, the only snag in the oath-taking was a little catch in Obama's voice as he uttered the word "states" in the phrase "president of the United States."
Even the parade planners learned a thing or two. They made this year's floats shorter, to improve their turning radius and allow them to move along Pennsylvania Avenue at a faster clip.
Even so, the parade ran long and ended past sunset, well after Mrs. Obama and the girls had bailed out.
Shelia Thomson, of Washington, hung in there to the end — but thought it too much.
"There's no reason these kids should be participating in the dark," she said of the marchers.
Some glitches were inevitable.
Malfunctioning speakers made it nearly impossible for the flag-waving fans stuck in the overflow section near the Washington Monument to hear what the president was saying.
"You're in the IT capital of the world: How can this be so hard?" a frustrated Smart demanded.
But even there, good will was in evidence.
"It does take away from the experience, but it's so minute, compared to being able to raise the flag for Obama," said Anna Johnson, who came from Decatur, Ga.
The party scene for this year's inauguration was more muted: Fewer big names. No concert on the steps of the Lincoln Memorial. Two official inaugural balls instead of 10.
But an expected 40,000 people crammed into the Washington Convention Center for those two balls, and there was still plenty of star power in the entertainment lineup.
Jennifer Hudson sang as the Obamas danced to "Let's Stay Together."
The Obamas and Vice President Biden and Jill Biden took a spin on the floor with selected members of the military.
Obama danced with Air Force Staff Sgt. Bria D. Nelson, and the first lady with Gunnery Sgt. Timothy D. Easterling of the Marines.
Biden danced with Army Staff Sgt. Keesha Nicole Dentino, while Jill Biden's dance partner was Navy Petty Officer Patrick Figueroa.
The first lady's custom ruby-colored gown as well as her Kimberly McDonald diamond-embellished ring and Jimmy Choo shoes will be here and gone — donated to the National Archives after the balls.
Late Monday, Stevie Wonder ran through crowd pleasers such as "My Cherie Amour" and "Signed, Sealed, Delivered" as small groups of fans danced on a big dance floor.
Also performing earlier in the night: Alicia Keys, in a flowing red gown. She planted herself before a piano and dished up reworked lyrics to "Girl on Fire," declaring, "Obama's on fire." Brad Paisley, too, revised his lyrics to fit the occasion, and began by thanking the troops "for keeping us safe."
That seemed to help make up for the cash bar and measly food — pretzels and snack mix — but it didn't satisfy everyone.
"You diet for weeks to get into a dress, and then they give you pretzels?" said New York's Caitlin Kelly, 28. "I'm gonna get tipsy fast."
Associated Press writers Matthew Barakat, Alan Fram, Dave Dishneau, Thomas Ritchie, C.J. Jackson, Donna Cassata, Sam Hananel, Kimberly Dozier, Darlene Superville, Matthew Daly and Calvin Woodward contributed to this report.
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