Overall we had a very good stay. Location is nice, close to the station, walking distance to everything you need. Apartment is spacious enough for 5-6 people and de code check-in system is nice, because no hassle with 'who has the key?'.
Some cons though: the appartment is nothing like the pictures! Not even a little close.
Also, the communication from smartflats is very very unclear. There is a portal you need to login, which isn't really working. They say you can contact them 24/7 but aren't responding to whatsapp or e-mail. In the end it all worked out fine, but it wasn't a smooth customer experience.