The locking mechanism has proven faulty to an attack on the cylinder. Kryptonite makes a small motorcycle disk brake lock. If you have a Quadra Chain with a Pierre lock, keep the chain and get the Kryptonite lock. If you're just starting out, you can buy the chain and lock set put out by Kryptonite. A cable is pretty easy to cut though, a bit of time with a wire cutter will do it.
Chains are far better.
It makes it harder to sell. Plus my bike looks like a piece of junk. I stripped off the paint and let it rust a bit. I grease it to keep the rust from pitting. A patina is okay, but the orange flaky stuff will eat through the steel pretty fast.