If it extends the battery life by only 10%, it is almost certainly *not* worth it. Priced at $2.50, it's appearance suggests a relatively flimsy product that's unlikely to last very long before you break it. Looking at the most popular AA batteries on Amazon, price per cell is just 24 cents.
That means a 10% increase in battery life is saving you 2.4 cents per cell, so you'd have to run 104+ cells through each Batterizer you need to buy before you first break even. (And most products, in my experience, use at least two cells, suggesting that you'll need multiple Batterizers and will have to run multiple hundreds of cells through them before you break even.)
Add in the fact that despite Batterizer's claims, the deeper you drain a battery, by far the more likely it is to leak, coupled with the fact that the kinds of things that are likely to leave any significant power in the cells in my experience tend to be those which drain power very slowly, and the chances of you saving any money with Batterizer are zip. This is a product for morons who lack the ability to think critically: No more, no less.
