I bought this for my grandson, but put it through its paces just to test it. I really like this unit, and am thinking of getting one for myself! My only issue is with the battery compartment: The two 9-v batteries fit in the compartment very snuggly - so tight that they are difficult to get out. I solved this by clipping a short loop of quite thin nylon cord between the posts of the last battery I install when attaching the snap-on harness. I then make sure the loop extends above the battery and under the door. Now to remove the battery, I just pull on the loop and the battery pops right out. The other battery is then easy to remove. This is my solution, so do at your own risk! Remember to install the batteries posts-down, and keep the harness wires toward the short sides of the batteries....you will understand when you try it: There is more room along the length of the opening than the width. Also, it seemed to me that Energizer batteries fit better than some others. The other issue is - as quite a few folks mentioned - the battery door can easily be dislodged in the field and lost. What I did is first put a piece of neon orange tape on both sides of the door - easier to find if lost. I also have a large rubber band that is stretched around the unit to pin the door. I am thinking of replacing the rubber band with some arrangement of Velcro strapping that would be less ugly and more permanent. This is a great detector for the price, and not just for kids!