seriously, part of the fun is just being contrary. everyone rides shimano, so by riding something non-shimano you distinguish yourself. same thing as riding something besides a trek or cannondale.
In use, I have found my mostly chorus (some record) drivetrain to provide crisper shifts and require less routine maintenance to keep it running. so far I haven't found any plastic parts in any of my campy components which I think is a key reason for the reduced maintenance. it's also been my experience that shimano parts are designed primarily to be disposable. if something major goes wrong you throw the whole thing out (sti lever, bb, rr der...) but the campy parts are designed more like racing car components, to be routinely rebuilt. the tolerances and precision of the campy parts seem to be of higher quality, see Dan's comparison or the long comparison on
www.totalbike.com. I believe record edges out DA in the weight category, though we'll have to remeasure once each companies '04 lines are out. there's also how you feel about materials. shimano shows no interest in carbon fiber (or modern headsets!) but does some nice work with aluminum. Campy is pretty much defining themselves by carbon fabrication.
on a road bike the ergo levers are the lynch pin. they are simply miles ahead of sti. the feel is positive, even after months of use (where shimano levers always feel very loose and rattly after a break in period, to me), and you can shift down up to 4 and up, up to 8. yes 8. crest a hill with sti and your going "whack, whack, whack, whack, whack" trying to get a gear for the downhill. with campy you just mash the lever down and stomp.
of course, at the end of the day, it really doesn't make you faster on race day. both obviously get the job done, but for these reasons I easily get my moneys worth out of spending a bit more in the beginning. the time saved in maintenance and part replacement later probably makes the initial investment a wash over the life of the bike.