The new amenities in the 20-room home include WiFi, encrypted to keep out Britain's nosy press, a panic room, day and night nurseries for Prince George and separate bathrooms for the prince and his wife, Us Weekly reports. Middleton, now the duchess of Cambridge, worked on the renovations while she was pregnant.
The apartment was once occupied by Princess Margaret, who died in 2002, and had been empty for some time. It also required removal of asbestos.
A former resident of Kensington Palace, where William and his brother, Prince Harry, spent much of their childhood, says it is actually a friendly place to live.
"It's a bit like Melrose Place," said Victoria Arbiter, the daughter of one of Queen Elizabeth II's former press secretaries. "You can knock on a neighbor's door if you need sugar."
Darren McGrath, who worked as a chef for William's mother, the late Princess Diana, predicted the young family will be happy in their new home.
"The baby's going to grow up running in the same gardens and hiding places William and Harry played in," he told Us.