I've been reading about other technology companies besides Apple doing this as well. Element and Vizio, two value-tier (think Wal-Mart and Target) flat-screen TV manufacturers have major assembly plants here in the states. They cited a combo of labor, shipping and duty being cost-ineffective at their price levels to make and ship from China.
Interestingly enough, The Atlantic just ran two long articles about the return of American manufacturing: http://www.theatlantic.com/magazine/archive/2012/12/mr-china... and http://www.theatlantic.com/magazine/archive/2012/12/the-inso... . Both are worth reading in full.
Clearly we're not going to get back to the 1950s, when manufacturing provided much of the U.S.'s employment base. But we're still substantial gains in the sector, and the belief that outsourcing always makes financial sense is disappearing.
Apparently, it's cost effective to assemble products in the US that incorporate large LCD screens. Apple was already assembling BTO iMacs in the US, and now some standard iMacs as well.
iPhones, iPods, and iPads are a different story, as they're a lot smaller. An airplane can fit a lot more boxed 9.7" iPads than it can fit boxed 21.5" iMacs – 28 times, to be exact (I just did the math.)
As for Steve Jobs' remarks, it seems he wasn't talking about iMacs but about iPads, iPhones and iPods:
"As Steve Jobs of Apple spoke, Obama interrupted with an inquiry of his own: What would it take to make iPhones in the United States? Not long ago, Apple boasted that its products were made in America. Today, few are. Almost all of the 70 million iPhones, 30 million iPads and 59 million other products Apple sold last year were manufactured overseas. Why can't that work come home? Obama asked. Jobs' reply was unambiguous. "Those jobs aren't coming back," he said, according to another dinner guest."
http://www.heraldtribune.com/article/20120123/ARTICLE/301239...
Manual assembly of the iPhones isn't coming to the US, nor is it staying in China.