We stayed at Guillaume's apartment for our second leg in Paris.
PROS:
Centrally located in Montemarte, metro is just 1 minute away and it's easy to get to most locations in Paris. There's a lot to do in the neighborhood, with many places open past 1am. Moulin Rouge is nearby. The apartment itself is nicely decorated and there are nice mementos of Guillaume's travels. We had some issues (below) but were able to get a response from the apartment caretaker, Mathilde.
CONS
Checking in wasn't smooth. I was told to go to a lockbox at a restaurant 6 blocks away. Not such a big deal. Told my friend to wait for me with our luggage at a restaurant across from the apartment. What was a big deal was not being able to access the key because the lockbox required a code that I didn't have, supposedly sent via an email that I never received (checked inbox, spam and trash folders). After traveling through the morning, we were exhausted and just wanted to be able to relax. I contacted the apartment caretaker and after going back and forth, she was able to reset the password. Aside from the lockbox issue, there was no mention in the post that this was a 3rd floor walkup. Ok we soldiered on, but it would've been nice to be alerted that there's a small lift for luggage which we realized after the fact. Flat had no toilet paper or paper towels. Contacted caretaker and she seemed surprised and offered to reimburse us. No iron. My friend immediately spotted a dirty flat sheet on her bed that was stained with some brown stuff. There were notes throughout the apartment indicating what not to touch but no useful notes on how to work the stove (which seems simple enough until you try to use it) or the jet tub. The apartment seems to have allergens in the bedrooms and lingering on the couch, almost as though a pet lives there. We both woke up congested each morning. WIFI was a bit spotty.
I think what would be helpful is if Guillaume or caretaker checked the apartment to ensure all essentials are there (iron, toilet paper, paper towels, bath towels that are big enough... and I'm a skinny girl), that that lockbox email had been sent or to indicate the code in the Hostnfly web app, that the flat is cleaned between lodgers, annoyances I'm sure Guillaume wouldn't want to encounter during his travels.