Just finished inputting the whole route into Garmin Connect to load on to my brand new toy. The prospect of doing that for each ride was one of the things that had put me off investing in a GPS until now but I found it to be very useful exercise. I always look at a map before any ride to get a rough idea of where it's going but keying it in turn by turn has imprinted most of it on my memory, which can't be anything but useful on the ride itself. I haven't ridden the new version of BCM so studying the last 160km was helpful.
However, I will still be carrying a route sheet and map - just in case!