Icarus, if you read what I said, I said ideally you wouldnt deviate from the plan. I also said that computers are great for if something DOES go wrong.
Computers aren't there to give people the idea that they don't need to plan, and where possible stick to that plan. But a lot of people use a computer to plan their dive as they go along. As you said, shit happens, and that's where the computer comes in.
How you plan the dive isn't the issue, providing you do it BEFORE you get in the water. Using your PC to plan it is fine, saves you having to do all those sums up in your noggin, PROVIDING you know how to do the sums yourself, and you make sure the numbers the computer gives you are reasonable. The point is if you plan your dive, you've planned it for a reason. Follow the plan through. The computer is there for if you decide during the dive that for some reason or other there is no point staying down any longer, and it then gives you the deco stops you need to do.
Matt