I'm by no means an expert on bike locks or security, but I had a Kryptonite Evolution...I think the series 4...and the key broke off in the lock. I read up on how to beat locks and I tried EVERYTHING on that sucker...I used freon, I tried picking it...EVERYTHING. Nothing made a dent. Eventually my father came up with a generator and a circular saw. The lock broke the blade after about 10 minutes. FINALLY...we got through it. It took a solid 20 minutes of cutting, and this was with a loud power tool shooting off sparks.

I think that's a pretty good deterent of a lock. I'm sure thieves know tricks that I don't, but I'm also sure that if a reasonably intelligent guy wasn't able to get through it and needed a generator with a circular saw...it's certainly a good level of protection.