I hate them with a burning passion. They take up half the screen on mobile, hiding the content I want to see, they often have annoying sounds & animations, and they are always present on pages where I don't expect them to be. A chatbox blocker would be a killer addition to the ABP browser on mobile.
Why not create a "Chat with us" page that loads the chatbox instead of force feeding it to every user who comes to your site, wasting bandwidth and load performance?