Is it neccessary? That's a pretty open ended question. It depends on the situation I guess. I'd say if you are hunting terrain that you are familiar with (i.e. your own plot of land that you know like the back of your hand) then I'd say spend your money on something else. If you hunting terrain that you are unfamilar and/or are hunting in a very isolated area, then it would be an invaluable tool. However, as people have already stated, don't totally rely on it. Know how to use a map and compass and bring it along.

Speaking of GPS's, has anyone read this months issue of Field and Stream? In their deer hunting boot-camp article they highlighted a new GPS unit made by bushnell that allows you to download satellite maps from their website. Looks pretty sweet.