charlesml3:
The slower ascent rate is indeed because we understand the physiology better. I'm not sure about whether the initial change to 30f/m was just to be more conservative or because of new findings, but current knowledge does indicate that 60f/m is too fast and may result in too much bubble growth and hence not safe enough.
As a matter of fact, deep stops are now being advocated based on new knowledge, which is slowing down the ascent even more than 30f/m. (But it is different from just a linear ascent.)
BTW, I can't help asking, do you feel the same way about seatbelts and airbags too?
It's all about statistics, and the fact that the huge majority made it through OK doesn't mean it's good enough. Almost everyone who used to drive without seatbelts made it through alive, but that doesn't mean that seatbelts are just useless encumbrances.
I must say however, that I agree that in a pinch you can make a safe ascent without a computer in most circumstances, especially if you do a generous safety stop at the roughly correct depth, which you can eyeball by looking at the surface. On top of that you will likely have a buddy to rely on. So unless you want to continue diving after a failure, I do agree that you don't really need backup instruments for diving within NDL's, especially with the fairly reliable instruments these days. (And when they fail they usually fail when you start the dive, when it's safe to abort.)
