I'd have to agree with Easy Limits. Everytime I've fished with downriggin, we seem to catch fish. Not sure how much the black box is helping, but for less than $100 you can't really go wrong. I got the box from Cabela's for Christmas. It was fairly easy to hook up and worked right away........I've only used it once, and at the end of the day I noticed that the reading went haywire on me. I turned the unit on and off several times with no luck...Finally said screw it and started heading in. About half way back to the dock, I stopped and tried it again and it worked...I'll have to wait till next time to try it again.
Bottom line, if it's broke, I'll get another one from Cabela's...I'm a believer....I think it might give you a little advantage.