I've had one for two years now. Not a single problem. The units lake maps are just the basic outlines (shoreline). The lake map chips are just ok. I bought the Navionics Hot Maps Premium chip. I thought that all of the lake maps had the (HD) 1 foot contour details. Not so.
I should have read the fine print a little better. Only certain lakes have that detail. But the unit itself is great. I still have to learn all it can do!