I had a Fish Hawk 840 for years, IMO it was a complete POS. you'd barely get 1 trip out of a probe battery and the numbers jumped around so much I had zero confidence in the data I was receiving. I eventually took it off the boat and replaced it with a Depth Raider. Couldn't be happier with the switch, it was a vastly superior unit and the coated cable is really not an issue as far as I am concerned. I got 6 seasons out of my original coated cable, and just replaced it last season simply because it was getting a little short from re-terminating every so often.
I've had my probe down over 160' and never lost signal.
FWIW, I've been on boats with the New FH X4 and they seem to have corrected everything I hated about it's predecessor, and it looks like a nice unit now, but I still don't think I would switch back personally. Both because my first experience left such a bad taste in my mouth and because I've sealed up all of the misc holes in my transom and I dislike the coated cable a LOT less than I do the idea of drilling more holes in the transom below the waterline to install another transducer.
Steve, unless you happen to fish in some isolated part of the great lakes without subsurface currents, your speed at the lure is most definitely NOT the same as the boat. I have seen well over 1.5 mph difference between speed at the ball and GPS SOG. Some times it only takes a few degree course change to drastically reduce the difference, but without the down probe, you'd never know your lures weren't running properly.. I'd do without my graph before I went without my DR. Once I find 42 deg for the bottom of my trolling spread, everything else is set up from there and knowing down speed is critical. Besides, we catch far more fish that we don't mark than we catch ones we do. That is because, the fish you see making a nice distinct fish arch on the graph is an inactive fish that is just hanging out down there. Most fish that hit, come in quickly and never mark on the graph unless you get streakers showing up around your marked rigger balls.
Tim