Some spells' effects are considered non-magical.Storm of Vengeance, combust.. the secondary effect of Meteor swarms. And since it's basically a natural effect from that point, like your pants being on fire you won't get sc bonus.. or protection from spells won't work.
I do belive it will add some extra dimension to the world/game if people in general knew more about the different saves. -For example people would stay out of places that they don't realy have any buisiness in. - many craftable rings/amulets and items that gives +1 upp till + 3 on different saves would be much more atractive on the market. As it is now the only jewelery people wear are +1-3 ability scores.
The question is not whether you as player should know this, but rather would your character actually know this and be able to make decisions regarding this? Would a your character know the DC save for a wail for example and therefore know to avoid certain things or not? Or would your charater chance it and find out he is not affected and therefore continue to chance it. Just my own personal opinion but knowing what creatures use what spells, and how they affect you and what the DC to save against them, is very much metagaming. Granted that if you are a wizard with years of study you would know what a certain spell is and what the effects are. And you might have a good chance to guess if you can survive or not. I am with Soul on this, it is way more fun not knowing what to expect and always be prepared for the unexpected than to analyse every piece of the game and make it a totally known factor.