Julien's place was excellent. It's literally across the street from a metro station for 2 lines, and is within walking distance of Gare du Nord (where one can get the RER to/from CDG Airport). There are also plenty of good restaurants nearby, along with a couple grocery stores.
As for the apartment itself, it is very quiet. The only noises we heard were the occasional siren and birds chirping in the morning. It was very pleasant. It is also well spaced. The shower area is a pretty good size, and we didn't feel cramped whatsoever when we were in the apartment. It also gets a ton of natural light (even in the middle of winter), which I really liked.
Check-in and check-out were straight foward and easy.
Overall, Julien's place was a great value and I highly recommend staying there if you have an opportunity to do so.