My urbanologist friend tells me that we can thank the gays of NYC for being frequent pioneers of gentrification. He says they have plenty of spare cash and like to spend it, they like interesting restaurants, and they like to make things look pleasant.
A generation ago, the gays moved into the West Village. Recently, moving into Chelsea, which was once a neighborhood which many conflated with Hell's Kitchen. Today, it is known as a semi-gay neighborhood (nothing in your face, though), but with plenty of young families with kids (strollers and moms everywhere), and lots of young straight professionals too (including a BD pupette, which is why I have become so familiar with the area. She is in a new Chelsea high-rise, with doorman, a business center, a gym and a cool roof-top garden overlooking the Hudson for parties - all you have to do is sign up for the roof-top).
Chelsea is full of old brownstones, and peppered with new high-rises. It's a short walk to Chelsea Piers, the Intrepid Museum, and the 12-mile Westside Greenway (for biking, running, and hiking) which runs along the Hudson River from the Staten Island Ferry to the George Washington Bridge. Now there is the High Line "park" too, which will run all the way to the Meat Packing District.
(The Upper West Side, where I dwelled for a while, has come a long way too in the baby stroller department, but it never quite needed gentrification. It was always a mixed area with all of its grand pre-war buildings and brownstones. Its SROs are gone now, though, along with the street crime.)
One could spend a lifetime studying the changing neighborhoods of NYC. Curtis Sliwa knows it all.
Brownstones like these in Chelsea now go for 2-4 million: