My 1st couple of races were on a borrowed bike with bar-end shifters. Coming from road racing on STI's, they were very foreign. I felt like they got in the way of the transitions and taking my hand of the bars to shift was a little dicey at times. I did love the simplicity though.
I'm racing on STI's now While I like the idea of bar-ends for touring or just riding around, I don't think I would go back to them for racing. There just so much going on in a race, especially during the mad starts, that shifting without having to think about it is important to me.
I think the only way I would run bar-ends again is if I ran a single ring, and cut the bars on the right side down so I could reach the shifter from where my hands would be in the drops. Actually, that would be pretty cool...