I'm surprised that you wish to give up the GPS. Having a recorded track that you can later review after your ride will let you see what you actually did instead of just believing the tales you might want to believe about your ride.
I find them very valuable so I can look at certain segments of every ride and see if I improved or not from the other times. It's not easy to look at your watch and get tenths of a second at that bottom of a hill and then again when you are cresting the top and do the mental math while continuing to ride.