An overall great stay and good value for the price you pay. The apartment is a really beautiful space and the location is good. Saint Gilles is a very nice area and the city centre is easy to reach by either subway or foot (a 30 min. walk).
Some minor annoyances were the following: the floor is creaky and the downstairs neighbours seem to be easily bothered by it, so one has to step lightly - it might be a good idea to bring some soft indoors footwear (or just walk on socks). During the weekends it can get quite noisy out on the street, so earplugs might come in handy as well (there was no noise on weekdays, though). Lastly, the showerhead didn't stay in place very well so taking a shower was tricky, but Gwen was aware of this and did inform beforehand.
Gwen is very sweet and hospitable, and quite easy to reach. Her English is also very good in case you don't speak French. Would absolutely recommend the stay!