I had a pretty sweet bike with presta valves I built myself. GT frame with amazing manitou front shocks, carbon fiber handlebars, aluminum rims, seat post, top tier derailleur, shifters and gears.

Bike was stolen from my university while it was liked on a bike rack with a security camera pointed at it. (It was locked with a kryptonite u-lock too.) Obviously school security and the police didn't give a shit. So I called around all the local bike shops and gave them the description, and the numbers stamped on the bottom of the frame. The shop about 5 blocks from my school called me to come pick it up. The thief brought it into the store to get the tires inflated because he couldn't figure out how the presta valves worked.

I loved them before that, because I found they leaked less than schrader valves. After that incident I am presta 4 life.