Been there, done that.
Something that I forgot to mention in my post, and that Lamont alludes to in his post, is the utter importance of gas management. Dive with a computer or without, but take the time to
fully understand the importance of rock bottom. Always leave yourself enough air to deal with anything that might crop up on the dive. Just dropping down to 100 fsw and staying down there for 20 minutes because someone said that equals 120 is idiotic if you don't have enough gas left after those 20 minutes to get both you
and your buddy to the surface safely.
Teaching real gas management is sorely lacking in the dive education industry in my opinion. I know that I had NO idea how to "get back to the boat with 500 PSI"... heck I had no idea what "turn pressure" was until I dove with NWGratefulDiver and he explained the concept to me.
All this talk about computerless diving is great, but in my humble opinion understanding gas management is FAR more important in the long haul.
Jimmie