It amuses me that most of the negative reviews for this product are from people complaining that it is not easy to unlock. Isn't that the point? If you're choosing to buy a lock that doesn't rely on a combination, then it needs to incorporate a mechanism that is still somehow difficult enough to deter theft. Thus, this product.
Here's why I gave this product 5 stars:
* IT MET MY NEEDS -- I wanted a lock for a backpack that I intended to wear at all times during daily city travel and tourism. I was mostly looking to deter pickpockets and opportunistic thieves from unzipping my backpack when I was in crowded areas.
* WHEN UNLOCKED, I DO NOT HAVE TO HOLD ONTO THE LOCK -- A lot of small combination locks are designed to loop a strong cord through the holes in zippers. Unfortunately, when you unlock them, that means you have to do something with the lock itself: either attach it to one zipper, put it in a pocket, or hold on to it. Not this lock. The two halves remain independently attached to their respective zippers, even when they're unlocked, which actually makes it easier (in my opinion) to switch from locked to unlocked.
* IT'S NOT DIFFICULT TO UNLOCK IF YOU KNOW WHAT YOU'RE DOING -- Despite what some reviews may say, this lock doesn't require a Ph.D. in rocket science to unlock. It's confusing and time consuming enough to deter a thief or give you the time to realize that someone is touching your stuff, but once you know how to unlock it, you know. The only downside to the product is that it doesn't include directions to help you figure it out your first time, but luckily you can find them here on Amazon. If you have dexterity issues with your hands, though, then then this might not be the product for you.
Overall, it does a pretty good job of doing what it's supposed to do.