North Carolina
I agree completely with what everyone here is saying about North Carolina, and I love it. They clearly are head and shoulders above everyone else at this point, and I expect them to be at an even higher level entering March Madness. I think most of us would agree about that with the sick talent level UNC has.
Why do I love it? Because ESPN now has their 24-hours-a-day "theme" for the rest of the college basketball season. ... "the unbeatable Tar Heels." We're going to hear about the Tar Heels ad nauseum for the next 3-4 months (get used to it), much like we heard about the "unbeatable Patriots." Whether UNC is unbeaten or not heading into the tourney, media outlets everywhere are basically going to hand them the title, if they haven't already.
As the last Super Bowl and many, many March Madnesses (Villanova over Georgetown comes immediately to mind) before showed, all it takes is one game. One. Not a series of games like the NBA, one. And one serious injury to one of UNC's most important players (i.e. Lawson, Hansbrough) at the wrong time (think Kenyon Martin/Cincinnati in 2000), one bad game by the Tar Heels and/or one "out-of-their-skull" performance by a supposedly inferior opponent is all it takes.
Roy Williams is an excellent coach, he'll have his squad prepared, but the NCAA Tournament is an entirely different animal than the regular season. Get the Tar Heels in a tight game in the tournament, maybe they start thinking about the last two seasons when they fell short of what a lot of folks thought was "their championship" to win? As one great philosopher once said, "Ya'neverknow."