This is a bit of breaking news, first picked up by Marc Ambinder:
Primary Choices: Hillary Clinton
The potential upside of a great Obama presidency is enticing, but this country faces huge problems, and will no doubt be facing more that we can’t foresee. The next president needs to start immediately on challenges that will require concrete solutions, resolve, and the ability to make government work. Mrs. Clinton is more qualified, right now, to be president.
So there you have it. The endorsement of course gives credit to both Obama and John Edwards as great candidates, but chooses Hillary as the best to lead the country right now.
Note that they address Obama's candidacy as one full of hope and promise, but lacking in specifics. John Edwards, on the other hand, is called a flip-flopper or in murky waters, only with much better writing then I can manage.
On the Republican side, they endorse John McCain. Ambinder jokes that this may hurt more then help McCain, so maybe there's a plus side for the Dems here?
UPDATE: For those of you who say this is expected, I give you the always excellent Ben Smith:
The endorsement won't sway a lot of votes in South Carolina, but the editorial page has become a more a voice of well-educated progressives -- who might lean toward Obama -- than of the Democratic establishment, and so it offers Clinton a useful boost, and one on her adopted home turf.
AND from profmatt in the comments, the list of NYT Editorial Board members.