Huge. Beijing is huge. Even the CBD area seems huge. Despite the massive skyscrapers there still seems to be plenty of open space, unlike in Manhattan where sunshine on the ground is a rarity unless the street is perfectly aligned with the direction of the sun.
Expensive. Not as much as New York overall, but certain items are as expensive or even more expensive. My rent is about 1/3 what I used to pay in NY, for an apartment that sells for about the same as what my old apartment in NY would sell for. But there are certain things that seem to be double what I am used to paying in the U.S. Overall my preliminary estimate is that 400k rmb per year after tax is what it takes for a family of 4 to live comfortably in Beijing in a rented apartment with no luxury purchases and still have just a bit of money put away as savings, but whether that turns out to be true remains to be seen.