If your talking about mine, it brakes extremely well compared to when they were attached to the drops because of the leverage. Shifting is a bit annoying, but plenty functional. If you have higher end STI shifters I would imagine it would be much less cumbersome. Mine is sora shifters so they don't have the paddles under the brake levers, just clickers on the inside. As it is, up shifting is easy, but down shifting I have to reach; if you use the other variety (with paddles under the brake levers) it should be easy either way.
It was a bit of a pain to get the cable routing perfect, but other than that setup was pretty easy. Wish I could shift without moving one of my arms out of the aero bars, but it will do for now.
I can get you some better pictures if you need, and feel free to question away.