Being the main shopping and commercial district, Causeway Bay is surprisingly lacking in decent bars.
If you want to go to a bar which is sort of decent and on the GROUND floor (as opposed to up a commercial building with windows that cannot be opened), you can go to Inn Side Out which is near Lee Garden on Sunning Road. I however don't like this place as there is always a big queue for tables and it is the sort of pub which allows you to throw peanut shells on the floor and I just hate that.
I recently discovered some pretty decent ones (with outdoor seating) - if you know where the LCX mall is, it is near there. The exact location is the area between Paterson Street, Cleveland Street and Kingston Street. Between the residential buildings there is a pedestrianised area with bars and restaurants.
The closest MTR station is Exit E. As you go out, walk on Great George Street (pedestrianised on weekends), Eastwards towards the Victoria Prak. Turn left at the first junction facing the Pearl City cinema. That is Paterson Street. Walk along Paterson Street for one block until you come to the next street called Kingstone Street (with an Agnes B in the corner). Turn right into it and immediately you will see the restaurant/bar street on the left.
It is nice, and it is the place closest to an apartment I just bought. I am just discovering the area now.