I just put in a downs an on my boat, it's pretty neat. How useful it is I'm not sure yet. If you go for stuff near break walls I can see it being really useful. I typically leave it on traditional scan for walleye. The one issue with downscan is you need to be close to the finder to read downscan. I can read the arcs from any point where I fish in the boat just fine, but have to be almost sitting in front of the downscan. I also have one of the smallest screens they make.
At speed we get a little interference off the port side. There is a water wash down filter that dips down off bottom that i think produces turbulence that it picks up at any speed over marina speed. If I were to install the transducer again, it would probably be where it is now. I don't think there's much I can do to get rid of the turbulence.
The other con is it shows what you already passed. So it's not too much help navigating unknown low spots like marinas and small rivers.
My advice after spending 3 hour routing a transducer wire through a boat without being able to see anything is this. Took me about 6 total, wiring, drilling new mounts, bringing wrong electrical connectors, wrong fuse, etc etc.Do you want to install a new transducer who's coupling will get caught on everything when you try to snake it through your boat, then I'd say you want it enough and should buy it. Otherwise I'd buy an upgrade that could use my current transducer if possible.