This unit was the first place I stayed when moving to Montreal - my partner and I lived there for 3 months while getting to know the city. I will attempt to review two aspects separately: Samuel as a host, and the unit. I'll add a tl;dr (too long; didn't read) at the end summarizing my recommendation.
Review of Samuel: Terrific. He was extraordinarily responsive, would send a repair-man promptly upon request, and genuinely wanted to help at all times. He really was a great host, and I highly recommend him.
Review of the unit: First, this unit is in a great location. Right near downtown, we were able to explore festivals, bars, events, museums, all conveniently within walking distance. Definitely ideal for newcomers or explorers. Second, the building itself is a big dingy. Smelling quite a bit like smoke, the public spaces were not very pleasant, but thankfully this smell didn't make its way into our room. The laundry facility looked a bit sketchy, but the machines worked surprisingly well and seemed clean. The room itself was quite small, and not as "modern" as the description led us to believe. The tub regularly pooled water as we'd shower, even after the plumber came to fix it twice. The water pressure in the kitchen sink was hardly enough to wash dishes. The bed was particularly uncomfortable so we ended up getting a foam pad to put on top of it.
tl;dr: Samuel was terrific, and I highly recommend him as a host. This particular unit was not great, at least not for a long stay or if you'll be spending much time in the apartment, but perfect if you're in Montreal for a short stay and will spend most of your time exploring.
Good luck!