Im considering the 5 for my kayak this spring, yeah I know, on a kayak ;D. How is it to use regarding simplicity, Im all for reading the manual but I dont want to goto MIT to learn the thing.
Once through the manual and you're good to go for most everything you need. Adjusting sensitivity, speed, zoom, bottom lock, split screens, way points, and map use are all fairly straight forward. With that said, it is a lot smarter than I am, so it has capabilities that I'm still figuring out. I am enjoying the learning process. It's another cool toy to play with.
As far as using good electronics on a kayak, why not? I have an older aluminum boat that I have re-furbished. Some would say putting high end equipment on an inexpensive boat doesn't make sense. My answer to that is nonsense. I enjoy my boat and having good equipment makes me happy and improves my fishing. Isn't that what it's all about?