Just because the game has no HUD (Does it have no HUD? I read through the features listed in the Game Informer article thread but saw no mention of no HUD being one of the features.) does not necessarily mean a Call of Duty type stealth system. My guess is that they'd use some sort of more natural indicator to show that your health or magicka is getting low, but if you actually open the character screen, you'll still get a more detailed indication of how much health you have left. At least, I hope it's something like that. If they want to have things like health bars not visible on the screen for the sake of "immersion", it may not be a reasoning I necessarily agree with, but it's one I can understand. But there's no reason why I shouldn't be able to see exactly how much health I have from my character screen, and I doubt they're going to try to pull that off without using any HUD elements.
What is wrong with Call of Duty's health system? It lets you know you're dying without having to look at some bar. Now the regeneration, I wouldn't want. but it just seems kind of odd having to look down at a few bars to understand that I'm dying. It takes me out of the experience.
Needing to have blood magically appear on my eyes even if I haven't been hit in the head to know I'm dying is also kind of unrealistic. But the thing that really bothers me about Call of Duty's health system is that health regenerates instead of being healed by health equipment, plus, the screen effects used to show that you're low on health make it harder to see, and when you're low on health, you would need to not have a hard time seeing because if you can barely see what's going on, it's harder to avoid further damage. Other than that, a health bar still gives a more precise indication of how much more damage I can take than an effect on the screen.
it means no quest markers...maybe
It really doesn't, as long as there's still a map in the character screen, and I don't see how you could possibly make an open world game without a map. Then they could just have the quest markers only visible on the map, just because you can't see them constantly doesn't mean they won't be used when you open the map. Although I'd say that would be less intrusive than the way it is in Oblivion because I don't get an arrow on my compass constantly pointing in a certain direction as though the game is saying "Go here! Go here!" when I'm trying to explore.