We would highly recommend this loft to anyone but particularly families as has a great layout and there is tons of space, which is unusual in NY. We are a family of 5 (kids 15,12, 7) and stayed here for a week, so the two single beds for the younger kids and loft space for the man child worked well. Everything was nicely decorated and the kids really liked their room.
The location is great as traffic is a bit of a nightmare so jumping on the subway means you can be most places in at least half the time to catching a cab, plus it is a main subway line. Union Square itself is a good hub to stay in and there was a great farmers market on certain days. There is lots of good shopping walking up to Chelsea and Eataly is a great restaurant near the Flatiron building if you don't mind a 20 minute walk.
The living area is cool and there is another day bed out there. Having a kitchen is fantastic and there is a supermarket to the right looking at Union Square and Wholefoods to the left as most reviewers have mentioned. Having a computer to book and print off tickets was very helpful and the washing dryer also a plus. As a light sleeper, it wasn't too noisy at night as parts of NY can be and the road out front not one of those main ones despite it being Broadway (but where it is tapering off).
I hadn't booked through VRBO before so was a bit nervous but everything worked out perfectly and Harriet does live above on another floor and there are only about 4 apartments in the building. It does look pretty run down from the front but I did hear this was a tactic of apartments not to attract any unwanted attention. Having looked at many hotels and apartments to stay in, we were really happy with this choice as it is hard to accommodate 5 people. Stay here, you won't regret it!