We bought our timed tickets to the top (about $27 each) in Dubai Mall ahead of time. If you wait to buy until you actually want to enter, tickets cost over $100. Tourists are permitted as high as the observation deck, around the 130th floor. At 1500 feet up, the deck is higher than the roof of the WTC (I took in that view in 1990) and the Empire State Building (which I ascended for the first time in 1962 when it was the world's tallest).
The elevator whisked us to the observation deck very quickly. I don't know why, but on this elevator your stomach doesn't do flips.
The view from the top this night was spectacular, even though the air wasn't clear. The Burj is surrounded by family-oriented tourist sites which you can see in this photo. The center is taken up by Dubai Mall; the fabulous water show is done in the lagoon on the lower right.
the water show