I find wires to be a pain. First you have this extra wire dangling around your handlebars/front wheel, then you have the zip-ties to hold the wire in place. Go wireless, before I graduated to a garmin I had this one (planetbike) - nice reliable unit:
http://www.amazon.com/gp/product/B00...YY8EHQ4558Q2BC
Nicest feature - the whole unit slides up to reset the trip meter. No hassle pressing tiny buttons multiple times as on other units I have owned.