I have porteur style bars with bar end shifters, and find them wonderful. My hands fall with the shifter at my little finger and ball of the hand, and I can shift effortlessly. On dropped bars, I could see how it would be more difficult.
Of course, on various other bikes I've had to change STI's because the ratchets inside wore down after constant use. Never had to do that with my Bifters. They just keep on going.