You need to be able to see, read and understand your computer easily at a glance. The trend, and it's a good one, is to make dive computers feature-rich, capable of providing a great deal of information to the diver. Your needs, interests, activities and fitness, as well as the conditions in which you dive, will change from year to year, even dive to dive. Your computer should be adjustable to fit these changes. Only in this way can the dynamic between the freedom to dive and the risk of diving be changed to best meet your current situation.
Dive computers gather data, make calculations and display the results to the diver.
Then the individual diver decides how best to use that data. Dive computers are tools to assist in the planning and execution of dives. Therefore the design of the computer should not take that control away from you. This means that the dive computer needs to be adjustable for differing conditions, that it should provide warnings and penalties for behavior outside of its program, but it should not lock the diver out unless the conditions of depth or time go beyond the computer's ability to sense and record that data. Instructions and prompt cards.