I've been using a Navman 4150 for years and it's been great. Yes there are echoes that show up as fishes but to be honest it could be anything really. When I'm working a deep lure, it shows the lure on the screen as I work it (not a fish symbol). So is very handy in showing what depth of water I'm working the fishing lure in. I never go with the fish symbols but would rather look at the sea bed features that hold fish.
The other thing I like about it is that it's got water temperature and shows the SOW (speed over water via a paddle wheel), when used with a GPS you can calculate the speed of the tide flow.
Oh and did I mention. . . I'm selling it in a couple of weeks