"Burj Dubai is now taller than Taipei 101 in Taiwan, which at 508 meters has held the tallest-building-in-the-world title since it opened in 2004," Emaar Properties, which is developing the Dubai tower, said in a statement. The Burj Dubai will be 141 stories tall.
The developer wants the tower, set to be completed next year, to be the world's tallest building according to all four criteria listed by the Chicago-based Council on Tall Buildings and Urban Habitat, which measures buildings to the structural top, the highest occupied floor, the top of the roof and the tip of the spire or flagpole.
This site, which keeps track of the Burj's construction progress, notes that the building's expected completion date has actually been pushed back to June 30, 2009. The pictures on that site show that there's still a lot of work left to do: the building's cladding has only begun to be applied, and interior build-out cannot occur until that is completed. But as long as the structure itself has reached the height milestone, I guess that's reason enough for the developer to celebrate.