To be honest I have a foot in both camps.
I agree with Gustavo that some of the best rides come from getting lost, however if you have a long ride or need to be somewhere specific with a deadline like a ferry then a satnav comes into its own.
I also like having the satnav on just tracking the route to give you an idea where you are in relation to where you want to go. Quite reassuring.
My pet irritant with the Tomtom Rider is the insistence on applying Faster, Eco, Shortest, Winding etc. to any downloaded map(track) which purposely avoids places unless you've added that point as a specific way point. I haven't managed to find a way to switch off this interference. And again like a lot of satnavs the literal application of 'shortest' which takes a short cut via a cart track/housing estate with speed bumps.
So I'll continue with a good map a written plan and the satnav. Maybe I'll get where I'm going and find some surprises too.