Wulfram said:On the other hand, the martial powers can be reasonably compared to real world capabilities,
This, IMHO, is where you go wrong--martial powers do not represent real-world capabilities, they represent the prowess of non-magical fantastic and mythological heroes like Odysseus, Beowulf, Cuchulainn, and Conan the Barbarian.
and the impression I have so far is that it even at the first level characters will be exhibiting abilities that appear preternatural at the least - which makes the characters seem too inherently special for what I would consider a gritty game.
Bang-on right--4E is definitely a game designed around the concept that PCs are Heroes in the classical meaning of the term--it's not really built to play "Sir Roderick the Guy Lucky Enough to Survive to Third Level." That's neither a slight against 4E or the grim and gritty play style--but yeah, if you want to be a hero just because you were lucky enough not to die against a goblin or two, you probably want to look for another game system.
(For the record, I think dark, gritty fantasy is insanely awesome. I also think the action-movie/mythological heroics of 4E are awesome. I will never, ever, attempt to mix the two.)