The location of the apartment is really amazing. There is a big metro and RER train station 5 minutes away, which means you are at most 30 minutes away from most major sights in Paris.
The 2.5 bathroom might be a bit confusing for some people - I expected at least one of the bathrooms to have a toilet in addition to the separate one, but it didn't. So there is in total one toilet and two bathrooms, each with a shower and two sinks. Not a deal-breaker, of course, but good to know beforehand. Because of this, I think the apartment is more suited for four people rather than five or six, but of course, this depends on your group and what makes you comfortable.
The communication with the CheckMyGuest team was easy and straightforward, so we had no problems in that area.
The only negative part of our experience was the cleanliness of the toilet and the bathroom floor. I did not get such an impression from reading the other reviews, so I'm willing to think that we were just unlucky here, and it's not always the case. The neighbors were also quite loud on one of the nights, and we could hear them until about midnight, which was quite annoying. The backs of the chairs on the big table were also a bit bent and they were not very comfortable for sitting, but if you're out all night, that should not matter too much.
All in all, great value for the money and apart from the cleanliness issue, I would recommend the apartment for a group of 4.