There seems to be a lot of folks in travel forums like this who don't like Brussels or think it's the Grand Place and nothing else.
I just returned from the city as part of a trip and wanted to praise it.
Yes, it has a layer of grime on it in certain locations and reminded me of visiting Eastern European spots like Budapest (I was there in 1993). Yes, there are homeless people and some shady areas. Yes, it's no Paris or Berlin or Madrid. (I'm really selling it well so far ;) )
There are also hills and winding streets and interesting architecture and shops and a diverse population, many languages spoken.
We took the Metro to the Stockel which is the last stop on the 1 line to experience the market there on a Friday morning (believe it is a few days a week) and loved the fruit and waffles and everything else it offered as well as exploring the neighborhood.
Liked the vibe and the vibrancy. The Grand Place is beautiful too.