Mat's place is really great. The bed is super comfortable, the kitchen is amazing - fully equipped with everything you need, the bathroom was super clean and also had everything we needed. Mat was quick to reply to my questions prior to the stay and the system for the door is very practical.
In terms of location, at first the place might look a bit random but it's actually really close to the subway station, shops, supermarkets and great restaurants. It's a great place for people who want to escape the very touristic and overcrowded Manhattan, as well as explore a cool neighbourhood. Williamsburg is quite hipster and offers many places to eat. Plus, it's super easy to get to Manhattan with the subway (5 stops and you are at the Empire State building).
Worth noting that Brooklyn is not so well connected - I didn't really have an idea of how it is so Willamsburg is better connected to downtown and Manhattan than to the rest of Brooklyn. Still, it's easy to get the subway or quick to take an Uber or taxi around.
We had a great time in New York, so definitely recommended!