Unless you only fish a certain river once a year or so I'd think you'd probably remember the holding water's features next time down on your own.

What's been intriguing to me about GPS is being able to accurately mark where you've found fish from a boat (with or without a guide) and then being able to bushwack to the area on those times you don't feel like dragging the boat or don't have time for a whole day's float or don't want to race an armada to the good water.

Bruce