I have heard a few guys say that the jam nut on the gas block loosens up and falls off. so i guess the easier adjustability and the nut not coming loose could be a good reason. but as you said, while the $107 isn't a big deal (i spent that much and more for dinner with my wife and daughter tonight, spending it on my xcr would be just as easy and more fun) I am not ready to jump up and buy it.
Now that being said, when the new barrels are available, i am sure i will buy the gas value then just to change it over for the mulitple barrels.