Petter's apartment is a great option for anyone travelling to and from Paris via train, as it is super close to both Gare du Nord and Gare de l'Est (and easily reachable via metro from Gare de Lyon too!).
I think it is ideal for someone who wants to be out exploring the city, and who is not visiting to spend a lot of time indoors. For example, there's no kitchen so if you're travelling on a budget and like to prepare your meals to save money—this is not ideal for you. The apartment itself is small, but very bright and has a relaxing terrace with greenery that offers some privacy. For us, this was exactly what we needed as we where only in Paris for 1,5 days and just needed a place to rest in comfort and that was close to the places of interest to us.
The area around the apartment has a young and trendy feel to it with plenty of bars, restaurants and cafés. For vegan or vegetarian eaters there are several good options in the area. Walking to Montmartre or Sacre-Coeur takes about 30 minutes, the Canal-St.Martin is just around the corner, and you're a 2 min walk from the metro station.