Excellent location, literally a 10sec walk to the Poissonniere metro stop and a gentle 10min walk to the Gare du Nord. Very close to lots of bars and restaurants too, and is in the middle of "Veggie Town" - so loads of options for great Veggie and Vegan meals.
The flat is clean and was perfect for the four of us (two couples).
NB there is no elevator in the apartment block, and the apartment is on the third floor. No problem for us at all (small bags) but might not be great with a small family or if you have massive bags.
We had an amazing couple of nights and I would highly recommend Pierre and Mery's place!