I stripped the front derailleur and large ring off the front. I crashed and bent the front derailleur, and then realized that the new front derailleur-less setup was actually perfect for riding around Chicago, where it's incredibly flat. Even a relatively small range in the cassette will do to get me up and down the hills here. So it's not really that there's a benefit, except some saved weight, it's more that having a front shifting system is useless for me.
I had this setup on two bikes. On the one that crashed, I had barends, and I just disconnected the cable but left both shifters on the bars. On the other, which had downtubes, I just didn't cable one of the shifters. You can get some clamp-on downtubes that have just one shifter, though. I think campy made one. And I thought I saw one at loosescrews.