Fish Finder - how much do they help?

I love knowing my depth and seeing the occasional fish arch fills me with hope.  Is it a necessity?  In most cases, No, but it does give you a tangible advantage...  Unless you're Jed, and then it's just something that gets in the way of outfishing people around him.  The Bastard!


-Mark-

Haha. I wish I was smarter, maybe I could figure out how to use them.