This lock was really good for the whole of 2 weeks before it broke. The key started becoming progressively more difficult to remove after the first week, and now it is stuck in the lock and impossible to take out, rendering the lock entirely useless. If you need a strong lock that will only last a couple of weeks, then I strongly recommend this product.
On the plus side, at least my bike was not stolen while using it, so it must be good at deterring thieves even if it isn't the best lock in the world. Also, it would have been more annoying had it become impossible to insert the key, since then I would not have been able to unlock my bike.