Overall satisfactory. The flat is nice, and bathed in light all day long. It's nicely located too, close to Gare du Midi, and in the heart of Saint Gilles. Well, equipped and comfortable, I had a pleasant stay there.
A few quirks and mishaps happened during my stay, but the host was responsive and helpful. For transparency: I was unable to get the thermostat to actually start the heaters, which, in February, turned out to make my stay a bit frisky; but I didn't try too hard either, and didn't really have the time to look into it further with the host.