The antigravity force that repeals the top from the base is magnetism.
The Earnshaw theorem is not violated by the behaviour of the Levitron. The theorem states, that no static arrangements of magnetic or electrical charges can be stable, alone or under gravity. It does not apply to the Levitron because the magnet is spinning.
The equilibrum must be stable, so that a slight horizontal or vertical displacement produces a force pushing the top back toward the equilibrum point ( demonstrated in the video at 0.58)
Slight changes of temperature will impact the behaviour of gravitation (every time there has to be an adjustement of the weight of the spinning top).
The top spins stably in range from about 20 to 30 revolutions per second. Its completely instable above 35-40 rps and below 18 rps. Howover, the spin lifetime of the Levitron can be extended by placing it in a vacuum and it fells after about 30 minutes.
