Good location next to Gare St. Jean, but it's a bit far from the centre of town. The centre is not really walking distance, and you need to take the C bus, which is fine - about 10-15 minutes.
The place was incredibly well equipped - Mat has clearly put a lot of thought into this. For example, the bathroom was completely stocked with essentials and more (e.g. deodorant). The apartment was quite comfortable.
Apart from the location, the only downside was electricity/water was out for a portion of our stay due to maintenance. Mat warned us in advance, but we had to go through a mediator on Airbnb Support to get some compensation out of him. I think he should've been more forthcoming about compensating us - not having water for half a day is incredibly inconvenient. But nevertheless, it was a pleasant stay, and I would recommend if you're doing a quick stop and like the convenience of being next to the main train station.