I love the idea of Campy - just about to upgrade to Centaur throughout, but that is going on an Italian bike. For me, it works fine, but I do not push the limits when riding. I go click, it changes gear and I am happy. Chum of mine has just put an 11 speed groupo on an 80s Colnago!
I can't stand the uber-modern lines of the Shimano groupsets, like my kit a bit more retro (alloy only, no visible carbon), but saying that, I hired an Ultegra equipped bike in Majorca earlier in the year and that was noticeably crisper and immaculate in performance terms. But, with the way I ride, I am prepared to sacrifice the extra performance I don't need to let me have the name I want.
Shimano on my MTBs all the way though.