For the price, you absolutely cannot beat the location. You can see Notre Dame from the sidewalk of the apartment. It is a very central location, right next to subway stops, restaurants, supermarket, etc. We also felt very safe in the area, and it was relatively quiet. Really cannot say enough good things about the location.
The a/c window unit was also a HUGE plus, as Paris was pretty hot when we were there in July. Most rentals do not have any kind of a/c, so we were very grateful to have it.
However, you get what you pay for, and there were definitely some drawbacks and disappointments to this apartment which for us overshadowed the good. Yes, the apartment is tiny, which was thoroughly communicated by the host, so we don't fault them that. The problem was that when the bed was folded out, you cannot walk around it. So if two people are sleeping in the bed and one has to get up in the middle of the night, the only way is to wake up the person next to you by climbing over them. We didn't realize this during booking. The bed was also pretty uncomfortable - the center of it is very sunken in, causing both people to sink towards the middle of it.
There were several issues with the shower, and there appeared to be mildew all over the bathroom ceiling.
Additionally, the listing says they have a "concierge", but this does not mean much of anything. We called the concierge only once, halfway through our 8 night stay to request one additional roll of toilet paper and a fresh set of towels. We were told that they do not provide these, so we had to go buy a pack of toilet paper just to use one roll. The "concierge" did not check on anything about the stay, other than asking what time we'd be leaving, and denied our one simple, reasonable request.
Perhaps these things would not be an issue to a guest who was staying alone, or guests who would only stay a few nights. They can be overlooked for a couple of nights when it means a great location at a great price. But by the end of an 8-night stay for two people, we were very frustrated by these things, and it didn't make for a very enjoyable stay.