Well, sometimes there are none. For business use, it allows you network sites together by dynamically using your existing data network. It allows you to run a single wire to the desk - no big deal for existing sites. I am not sure if this is good or not, but it tends to put more control of operations on the data team. For home use, it sometimes offers a cheaper local access line with some additional features. Overall, it is the future but it has some growing pains to go through.
