I use the Bizer app on my iPhone and it works fine. It can be a bit tough to see sometimes but it's not unusable. It has a feature for viewing in sunlight which makes it marginally better. But overall I love it, the GPS is great and has a lot of nice features for plotting courses, marking way points, etc...
The new Garmin maps are pretty awesome. They spent a lot of time and money re-mapping a lot of lakes with a lot of detail. It is a bit more $$$ but depends on what you are looking for as they do not have any of the markers or anything. Or you can buy a chip from Bizer that can be used on certain Garmin GPS units.
But most definitely get a laminated map as well, sometimes it's just nice to be able to grab a real map and check things out, I always have the map and phone out together
