Luckily for me my only bike stolen was a Peugeot mountain bike from 1984. Had it locked outside of the Chemistry building at UC Berkeley with what I thoght was a big, thick, secure cable. Well, it was big and thick, but not secure! I took the remaining piece of cable home and tried to cut it myself - it took about 30 seconds with a hacksaw.
Happily the bike was returned to me. Three years later a neighboring city police dept. called me to say they recovered my bike! Some kid was riding down the wrong side of the street at night with no lights. Cops pulled him over and did the usual checks. When they ran the serial # through the computer, bingo! So the lesson in this is to be sure to record your serial # and keep it in a safe place. Better yet, engrave or stamp your drivers license # on the frame. And if you ever have a bike stolen, be sure to report it. Yes, the police have lots on thier plates, and bikes oftentimes become low priority, but theft of nice ones qualifies as grand theft, so they'll act if they have the opportunity and right information.
I now lock with u locks or a New York chain. Whenever using a u lock, I be sure to remove the front wheel and run the U through both wheels and frame, filling up the inside of the U to reduce the ability to get tools on the lock. Mini U locks work great for quick runs into the store.