Interesting thought but the results weren't all that promising. I set both my car (BMW Z4) and the Plantronics headset to be enabled (set to 1) on this value and when I checked the Bluetooth menu settings it looked like both devices were enabled.

I tried a phone call to the i760 and the Plantronics earpiece was able to answer the call just fine but when I went down to my car it was unable to answer. I checked the values in the Bluetooth menu and right after that effort neither the car or the earpiece had a check in the checkbox. By the time I got back to my desk and checked again the Plantronics entry showed it to be enabled and the BMW entry was not checked. The registry entry for Enable for the BMW was also back to "0" while the headset entry for the Plantronics was at "1".

It acts like there are some pieces of code somewhere else that determine how these registry values are used/manipulated.

It is interesting to note that the car shows bluetooth properties for "handfree" while the Plantronics has setups for "headset". This is true for both for the registry values as well as the bluetooth menus.