I use regular housing clips on my Raleigh. They're pretty cheap and easy to find NOS or very good condition, especially if you aren't picky about which model (you pretty much have to be closer than 18" with 20/20 vision to be able to tell what brand they are anyway). The Campy and D/A ones I've used are slightly curved on the inside so that the edges won't scratch the paint. However, after having my frame repainted by Peter Weigle, I decided a little more paranoia was in order and cut thin strips of electrical tape to put under them. The electrical tape is visible a little bit, but I don't feel that it particularly detracts from the look of the bike any more than the clips and brake cable do anyway.
If you want to be able to easily remove the whole business, I'd say clips are preferable to zip ties because you can just unscrew them and screw them back on again. Of course you have to be careful removing them not to bend them too much if you want to remove and re-install them repeatedly. While I haven't removed the electrical tape to check, I seriously doubt that the clips have done anything to the paint.
Emily O'Brien
these days in
Rheinstetten, Baden-Württemberg, Germany