I converted my Campy double to a triple and see no difference in shifting on the cassette and if there is a difference in shifting on the front dr. it isn't very much. However, I have plans to replace my triple with a compact but for a different reason than shifting performance.

My triple is a 53/42/30 with a 13-26 on the back. I probably only use the 30 chain ring once or twice a year, but it is great to have it when I need it. I do go between the 53 and the 42 a lot though. Going to a 50/34 with a 12-29 Campy 11 speed would give almost the exact same range as the triple and the 53/42 has just about the same range as the big chain ring on the compact. So 98% of time I wouldn't need to shift the front dr. It would also reduce a pound or more from the bike.