Me and my boyfriend had an excellent stay @Guillaume's place.
The appartement looks beautiful and has anything you need for a great stay in Paris (including a coffeemaker, full kitchen for your breakfasts, a rainshower (!), and also the Metro/supermarket and bars nearby etc).
I think I must say too though that the floors of the appartement are very thin (beautyful old wooden floors). When the upstairs neighbours came back on our second or third day in, we could hear a lot of running around from the kids.
Nevertheless: great stay! Excellent location too and communication with Guillaume was fast and fun :)