Dave: I really don't understand the benefits...
Basically, a increasing number of (rich or very geeky) people want a Home Automation system. Having a computer that control the whole house appliances, curtains, heating, lights, burgler alarms, watering the plants, etc...
Today, if you want a system like that it does not integrate that well with your B&O AV network... and you needed to have a Beo remote for your AV and another remote for controlling the home.
With this gateway, you can add commands to your Beo5 menu, the IR receiver from your B&O TV, hifi, etc... will get the signal and send it to the ML bus. Then the Gateway will pass that command to Home Automation computer that can then execute a macro and turn the lights down, the heater up, close the blinds, start the dish washer...
You can add many of this commands to the Beo5.
As it is a two way system, the Home Automation system can query the status of your equipment, detects if you are listening to music, and can control your B&O equipment as well, like turning the TV on in the bedroom, etc...
You can imagine that it can turn the TV off if you have not been in a room (presence detectors) for a while.
The other advantage is that if you have those controller screens in the wall, where there is a menu to control the house applicances, you are now able to add menus to these screens that will control the B&O stuff as well.
One of the supported Home Automation system is based on the KNX standard,
You can see here (go through all the choices on the left) all the devices that you could control with such a system:
http://www.knxshop.co.uk/catalog/default.asp?id=000-001-1001