Even if you are just a casual gamer, this gizmo is a must. Calculate the average life of a battery, and the average amount of time you spend playing video games. Then imagine the money you spend on batteries. It soon adds up. Why spend more than you need? With this rechargeable unit, you can play games without worrying about forking out more cash for batteries. During gameplay when you receive the "Please reconnect controller" message, you just plug this in and continue playing; it charges while you play. When the red light goes green, it's fully charged, and you can disconnect the cable until needed again. I've found that when charged fully, it can provide at least 12 hours or more of gameplay. For me that is more than enough; it depends on how often you play. Regardless, it's far better than endlessly spending money on batteries.
A few words of advice: like all rechargeable batteries, it is best to fully deplete it before charging it; this extends its lifespan. Don't charge it until you really have to; during gameplay you may see those spinning green lights on your controller, indicating a low battery. Though distracting, this still means there's enough power to keep playing a while. Only when you get the "Please reconnect controller" message every few seconds, and the lights on your controller spin constantly, should you charge it.
Whether you're a serious hardcore fan, or just a casual gamer, you really need one of these; it'll save you a lot of dosh in the long run. Gaming is already an expensive business, and any opportunity to save money while gaming can only be a good thing.