I bought this lock as a replacement for a D-lock that I was sold with my new bike. Within 3 days of using my new bike someone tried to have a go at the original D-lock. Luckily they didn't get my bike but the lock was damaged and unusable afterwards. After some research I discovered the Kryptonite New York mini lock. Its an excellent lock, not only sturdy and secure but also a great deterrent. I don't think any bike thieves have even sniffed at my bike since I started using the lock.
On a down side what I would say is that being a "mini" lock means its a very snug fit to get it around my bike frame and the rack I'm attaching it to, as such some of the thicker racks are impossible to attach it too. Also, I do use the lock with a cable around my wheels which adds to the security but it also adds to the weight of the hardware, and this lock is pretty heavy.
Saying all that I would rather have the piece of mind that comes with the extra weight. Not a lock for casual cyclists but excellent for a daily bike user who needs security.