I came to Brussels for the weekend with my mum and Joost's place was perfect. It's so close to the Grand-Place (useful on a very wet January weekend!) and loads of nice restaurants.
The apartment was really clean, well equipped and we had everything we need - including some really useful guide books, which was fantastic as we didn't have a set itinerary of what we wanted to do!
Worth noting that there are a fair amount of stairs, so probably not for you if you have mobility issues (:
Joost communicated really well, and I'd definitely recommend staying here if you're in Brussels!