We don't use our CP for route planning. Its route and waypoint management are so deficient even simple tasks are frustrating, compared with the usability of PC-based nav software (I used to use Nobeltec and now use Coastal Explorer). Will try OpenCPN at some point, probably before I pay for my next CE upgrade.

One thing I love about CE is the ease of updating charts free, especially for the US. I use Navionics charts and find them to be superior to the built-in charts in my Lowrance CP, and sprung for the Navionics card (even though the Lowrance comes with the US charts) because the Lowrance CP showed me the wrong data (or missing data) frequently enough that I think it's unreliable.

I use it for cockpit on-screen chart reference and for the radar, mostly (having radar overlay in the cockpit is nice in low-vis conditions). Sometimes I use the sounder/fish-finder functions that are also built-in.