200/83 sonar, gps, chartplotter, and micro SD card slot is a lot of features for 199.00. With a 3.5 inch screen you will end up zooming in and out to distinguish waypoints that are near each other. If you do not have gps or sonar now this would be far better than not having it.
One thing to note is that these do not have internal electronic compass, they rely on GPS. This makes getting directly on a waypoint a little difficult at slow speed. As you approach the waypoint the direction arrow will swing around.