Strong points: easy self check-in and very good location. You can get to many touristic attractions walking (up to 30min walk). The neighborhood is good and has bistros and grocery stores nearby. OpenFlat was quite easy to communicate with, which facilitated things.
Weak points: it was less clean than I expected. Shelves were dusty and we didn't have hand towels in the bathroom. I informed this to OpenFlat.
Some people commented about noise in previous reviews. There is noise in one of the bedrooms when someone uses the bathroom, but honestly unless someone takes a shower at 3am, this shouldn't be a big deal.
Overall we enjoyed our stay.