Start with the “bad” (because, really, it is minimal): it’s a 5 floor walk up, and it can be loud late at nite. That’s it. Nothing else.
The good: everything. It’s a short walk from the flat to nearly everything: restaurants, shops, riverfront, parks, miradouros (scenic lookouts), Castelo São Jorge, Pink Street, everything. The roof deck has views that should charge an entry fee just to experience.
In short, if you want to be near Lisbon’s nitelife, this is where you want to stay.