I bought a Trek T2000 which has Uletgra after using Campag on all my road bikes for the last 10 years.
Echoing previous comment I found that the main difference is in the shifter:
1. I can't get a comfortable position for my hand on top of the Shimano lever. Either the lever needs to be so far up that I can't reach the brake on the drops or the bar / lever interface is uncomfortable. This was never a problem with any of my old / new style campag levers
2. I have rebuilt quite a few Ergo levers mostly when the springs fail or the mechanism needs grease or when I wanted to switch from 8 to 9 speeds. I have probably saved the better part of £500 compared with binning the Shimano levers
3. The Shimano rear shifting is very, very impressive in terms of smoothness, but it's no better in terms of function. The Shimano 'shift on release' mechanism is a bit odd. The Campag front is about the same as Shimano, but both systems need careful setup to work at their best.
4. The Campag levers have a brake release on the levers, while the Shimano ones don't. This doesn't matter if you use a complete system as shimano calipers have the cable release on the brake, but if you're using cantilevers (not v-brakes) on a tandem you end up with no quick release, which is a real PITA if you have wider than 28mm tyres and need to remove a wheel.
The rest of the groupset is different, but you get into theoretical benefits / personal opinon quite quickly, e.g. DA hollow cranks and outboard bearings (stiffer, but can sometimes fall apart and looks space-age) versus carbon Campag with standard bearings (lighter, lower rolling resistance, more traditional looks and compatable with all your other cranks).
My next plan for my T2000 is to fit some Chorus ergo levers, a chorus mech and 10 speed chain, then run this on a Simano 10 speed cassette as this works really well on my single bike, and is much cheaper than changing everything.