We had a really nice stay at Leo's.
The location could not be better, just a few minutes walk from Pompidou center and a few minutes more to Notre Dame. Public transportation is very easily accessible from the flat.
Check in was pretty easy, although the instructions could have been clearer.
The flat itself is really nice and felt Parisian. It is 4th floor walk up (which was not an issue for us).
I'm terms of room for improvement, I'd recommend reducing the amount of personal belongings visible to guests to improve the quality of stay.
Leo very kindly left us a bottle of wine to celebrate new year's eve and was available to answer our questions over whatsapp.