Williamsburg in Brooklyn is incredible. I've been to NYC a few times and this is easily the best location (even having stayed near Time Square in the past). There is a 15 minute ferry to Wall Street from the harbour for 2 dollars and one of the best craft beer breweries in the world 5 minutes walk away, right by the river. Bedford subway brings you to Union Square in 6 minutes as well. So yeah, perfect for visiting Manhattan, but also a great escape. Plus there's a lot of stuff in Williamsburg (definitely do all your souvenir shopping there rather than the busy centre!)
The place itself is a basement flat and dark. There is no option to make the place less dark, which I imagine would bother some (but frankly for me visiting NYC is all about getting out there).
We were 4 and were very comfortable in the flat. There's a good kitchen and all the needfuls.