I remember the days when you had to scour a map looking for the highest elevations and then perhaps missing one. There was also the posibility of uncharted masts, so the introduction of MEF figures for each map square really took away all the hard work.
For VFR you only need to look out of the window and have an idea where the high ground or masts are. MEF + 1000 feet provides a practical safety margin however; so long as you don't infringe the minimum height rule you can fly at whatever altitude you like. If the weather becomes an issue, current teaching is to do a 180 degree turn and go back to where you know its better. This is a skill test item.