I snagged a faucet adapter for my cornies. I secondary in my kegs, so it makes sampling a lot easier. Well, it's easier when I don't forget to close the tap before locking it on.
I haven't tried it with a cold and carbed up beer but considering I'm getting a nice head on a warm uncarbed porter, I imagine close coupling like that will cause foam.
The other reason I wanted to try the faucet adapter is if I go to a less-than-civil gathering with a keg, I can just yank the ball lock and faucet off together and stick it in my pocket to prevent unauthorized sampling.