So, I'm sure there's been a great deal of speculation about whether or not FFG is going to make marines resemble the fluff or not.
I took the time last night to review the Space Marine codex, and consider all the capabilities they're supposed to have due to their extra organs.
A short list:
Space Marines can breathe underwater.
Space Marines can spit an acid poison at their enemies, or use it to dissolve the strongest metals (Yeah, SMs can lick their way out of prison.)
They can eat the flesh of a creature to gain some of its memories.
They can cocoon themselves in a waxy substance (that protects them from hard vacuum) and enter suspended animation, for centuries if need be.
They have an extra heart, and an extra kidney, in addition to an extra lung. The extra kidney and lung are both pretty awesome.
They can taste-test substances for toxicity and nutritional content, in addition to being able to track by scent like a hound dog.
They have super-hearing (can filter and enhance different sounds, in addition to being much sharper than a normal humans) and enhanced low-light vision. They also have better-than-human balance.
I think it's pretty easy to wonder whether or not we get "wargame" marines or "fluff" marines. But, I think FFG is smart enough to figure out that nobody buys Deathwatch to play a trooper with some extra Strength and Toughness. Rogue Trader was crazy-awesome because they gave starting PCs a ship that could dominate a whole primitive world from orbit, was kilometers long, and had thousands of crew available to carry lasguns. I don't think there's a whole lot of reason to think they'll pull back from that and ***** out the Space Marines to make them "balanced" or "reasonable" or "not ******* terrifying."