One Union Square South is a great place to live,it is half a block away from all major subway lines. I live in a corner apt and the view is amazing . The only concern about it is that corner apartments are soooo cold. Staff is always helpful. They bring up all deliveries up to your apartment, even if it's 1 pound; they jump on a street to catch you a cab. Also, the building stuff made my move super easy, they would not let me even touch a box.
My favorite place in the building is definitely the rooftop, it's never crowded there: great place to study; have a glass of wine after work; invite friends for a BBQ on the weekend. The gym in a building is a bit small, but it has everything you need. Family room is quite nice as well.
My main priority while searching for apt was convenience and fast commute, and 1 Union Sq South was the best fit.