We stayed at Julien's in early January — unfortunately, the apartment had a recent leak from the heating system in one of the walls, so on top of cold seating/dining/bathroom area, it was also very smelly and mouldy. While Julien claimed to have only learned of the leak the day before (and later backtracked to "few hours before arrival"), it was still terrible to stay at the place with no heating to most of the apartment (only the bedroom was heated) and unhealthy air with a 3 year old child. In my experience with leaks like these, the wall between kitchen/bathroom corridor is soaked with water and will take at least a month to air completely after the leak is fixed.
The right thing for Julien to do would have been to suggest for us to look for alternate accommodation while staying in his place for free until we found a better solution — his place was not suitable for renting (broken heating in January, smelly, likely unhealthy, esp for a kid), so there should be no expectation of any income, and the best you can do is not mess up someone's visit. We probably would have been out the next day if he was fully honest about the situation — as we only established the smell when we came back in the evening after only dropping our stuff on "check-in", and then discovered that it was heating that was problematic late next day as we tried to air the place out. His friend Juan let us in and didn't mention any of the issues either.
Julien initially offered 100 CHF back (~12% of the full cost) and later 50% of the rental price (AirBnB fees excluded, so not 50% from our POV), but I am still disappointed that we were tricked a bit by the apartment being aired just before our arrival and not being notified that the heating is not operational in most of the apartment until after I enquired about it.
Provided the issues above are fixed (though honestly, I'd give it a month or two), Julien's place is in a really nice location (though there is nightclub music going on deep into the Fri/Sat night which others have mentioned) and place is a little bit more run-down than the photos suggest (but which one isn't? :). The lightning in the kitchen is barely sufficient to use in the evening, and you are only provided with 3 mugs so you'll be up for some frequent dish-washing if you like drinking tea or coffee. But the basic amenities (dish-washing soap too) were provided and you can even cook something if you are so inclined.
We did drown our sorrow a bit in the free chocolates Julien provided, but it was definitely not enough. Generally, if not for the unpredictable issues with the apartment, I am sure staying at Julien's would have been pleasant. But it's important for hosts to learn when their place is not suitable for renting too.