Everybody uses it, not only people from Bergen, but it is very unformal. You would not be looked weird at however, if you as a foreigner used it. The Norwegian language is very unformal, the formal words are no longer in use, but if you want to speak a bit more formal to an elder or in a business situation or something, I would not recommend using "ha'kke" "vi'kke" and so on, it is kind of childish.