Me and my girlfriend have had a very nice stay in Brussels at Harold place! We stayed here for one month, but we would have stayed even more if it was free.
The apt is way more beautiful live than in the pictures, it is small but cozy and with everything you might need (bedsheets, towels and kitchen stuff). The bathroom (with bathtub and sink) is small and divided by a curtain but the toilet is in a separate small room (from the other reviews it was definitely not clear). The bed is comfortable, with a really warm blanket, and the closet has a lot of space.
The position is good, close to the European Commission in a quiet but equipped area (bar, restaurants and supermarkets are all close-by, there is a metro station and multiple bus stops within 10 minutes walk).
Finally, a couple of words on Harold, the best host you can get: very nice, always helpful and fast to answer, he helped us, also by giving us a lot of advice on how life is here in Brussels.