Had a very good stay at Charles-Antoine´s place. It does indeed look slightly better than the pictures suggested when I booked. Would recommend his place for stays from several days to multiple weeks.
The apartment is nicely located - a Metro station (Thieffry) and a well-sorted supermarket are within 3-4 mins walking distance. If the sun is out, you may also choose to walk to Schuman (20-30 mins, depending on what is your exact destination), crossing the Parc du Cinquantenaire.
During my stay, WiFi was not always stable, so I used my private laptop as a hotspot. If you are a trainee at an EU institution, the fitting adapter should be part of your IT equipment (but consider that the EU PC will not allow sharing internet access). Otherwise you might want to make sure you have one. The internet access via LAN worked smoothly.
C-A and his family are very nice and great hosts. Also, he is responsive and cares for his tenant(s). One feels very welcome in his place from day one! :)