This is tricky, I had a very bad image of Brussels from scratch. The city looked like a dirty and weird 1970’s version of a developed city. Although I don’t really think I’ll return ever again(if I don’t really need to) there was some pretty good places to work like Cafe le Coq and Corica grand place (good selection of coffees, amazing taste and great internet but there are no places to sit inside).
The internet is good but the city as a whole is not, at least from my point of view. So, if you really need to go, you will be able to work.
Some pictures of my wanderings around Brussels: