I made the switch from Shimano Ultegra to Campy Record in February when I bought my new bike. The differences that I see are:

1. Once adjusted properly (it took one visit back to the shop after initially picking up the bike), I never had to make additional adjustments.
2. The gear and brake cables are run inside the handlebar tape, so there's no cables hanging out the front.
3. The hoods are much shallower than Shimano, so it's much easier to brake and shift when your hands are up near the hoods.
4. You can shift multiple gears at a time.
5. The brakes work much better (something that I didn't realize until I went out on the old bike one day -- it was shocking how much longer it took to stop the bike).
6. The shifting is nearly silent.
7. The campy record components are lighter than anything Shimano puts out.

Hope that helps,

Susie

p.s. Now that I've ridden with Campy, I can't imagine going back to Shimano.