Personally, I think this comes down to a difference in style. There's gritty, and there's "Grim and Gritty."
It seems to me that the direction Mearls is after with
Iron Lore is gritty, heroic, and (to a lesser extent) cinematic. Bear in mind that I've only seen the same previews that all of you have, and I have no magic insight into Mike Mearls' mind or intention. However, from what Mike has said, he was inspired to create
Iron Lore by the same stuff that "hooked" me on D&D to begin with. Given that, and some of his comments, I'm willing to take a stab at the "feel" Mike's trying for.
Earlier in the thread, Mike said
Iron Lore is a game of high action and adventure. Like most fantasy games, it draws inspiration from a variety of classic sources - Robert Howard, Fritz Leiber, Clark Ashton Smith, and so on. However, if you were to ask me which movie most closely embodies Iron Lore's design, I'd say Die Hard. John McClain is the prototypical Iron Lore PC - he's tough, resourceful, clever, and he takes a beating but keeps on going.
So, if John McClain is the epitome of the Iron Lore PC, the question needs to be asked as "what sorts of things can the PCs DO?" The point I was trying to make earlier is: arrow ladder is NOT a supernatural ability. It's a stunt - a trick. One that could be accomplished in the "real world" by a highly accomplished archer. I think the whackiest you'll get in Iron Lore stunts is something like a Jackie Chan movie, not
Crouching Tiger, Hidden Dragon. For instance, Jackie often scampers up walls quickly in his movies without using wires. Now, in the movies, he scouts the location and plans it out in advance, looking for this handhold and that handhold, and then he just has to execute it properly. Humanly possible, just not something most people could do "on the fly." (And Jackie often "screws up" some of these, just watch his outtakes).
And that's how I see an Iron Lore PC. They don't do anything supernatural, just things that you rarely see happen in the real world because most people just aren't accomplished enough to do it on the fly. Could they? As in, is it physically possible? Sure...if they worked at it a LOT. And by the mid-high levels, that's exactly what heroic PCs are assumed to have done!
So PCs are larger than life, and will be doing things you'd expect from Indiana Jones, John McClain, or James Bond (or the Three Musketeers, Zorro, Conan, or Fafhrd and the Grey Mouser if you want more genre-appropriate characters). At the highest levels, their exploits are legendary, and might approach the abilities of some of the "lower-power" comic book characters (Batman, Green Arrow, Hawkeye, Captain America) or legendary heroes (Roland, Robin Hood, or Hawkeye from
Last of the Mohicans).
At least, that's how I see it.