Current 14-18 year olds will only have known a Democratically controlled government (since they became aware of politics and such), so any mistakes made by Obama and the Democrats will hurt them significantly with the youth.
After Dubya, whom they will know and revile, they won't expect perfection from Obama. The youngest voters of 2012 will have been born in 1994; they will remember 9/11, which happened when they were almost seven at the youngest. They will remember the invasions of Afghanistan and Iraq. They will remember the grandiose stunt of the President fling a naval aircraft onto an aircraft carrier to a banner reading "Mission Accomplished" only to find out later that the war continued in Iraq and Afghanistan. Of course they will remember the subprime lending scam and real estate bubble coming to a bad end. Many will have recognized as young as age 14 that Sarah Palin was a political disaster.The "mission accomplished" event is probably not in these voters' memory.
They will also remember Nancy Pelosi, Chris Dodd, the huge deficits that they will have to pay off, as well as others.
If Obama fails on healthcare and/or raises taxes, they will become more cynical of politicians and trend to the right. Either of those is possible, though if they will actually occur remains to be seen.
Also remember, the youth who voted heavily for Reagan in '84, the youngest of which were 6 or 7 in 1972, lived through watergate. That hardly drove them away from the GOP.