I have one exactly like that one... and it has been a valuable tool to me as well... especially when everything you drop in the shop always seems to end up bouncing or rolling up under something.
I have also used it to find nails, screws, and other small metal objects in the grass whenever I've dropped them around the outside of the house or anywhere around the yard.
I love Harbor Freight and would definitely agree that it's money well spent and that it should be a tool around anyone's shop or workspace.