On the lethal/non-lethal, ghost/non-ghost issue:
What I dislike in stealth games is the possibility reload my save in order to execute the most silent and "peaceful" playthrough. I'm not casual enough to prevent myself from reloading my saves countless times until I got my mission as I originally planned...
I did that with Splinter Cell, Alpha Protocol, Deus EX:HR or Dishonored, MGS, even Skyrim. This is like an illness -- because of appetite for perfection, I can hardly enjoy stealth games anymore. Those games aren't designed for action anyway. If you screw up, you're dead. I wish you could screw up and find a solution to the fact you've been seen and purchased. This is a huge issue in game design in my opinion. If you're caught, you should be able to take an hostage and negociate for example. You should also be able to bribe or threaten guards...
Overall, they really need to rethink the save system. When I was playing Dark Souls I loved how the game didn't let me reload a previous save to undone a "bad" action (i.e. accidentaly killing a NPC). Do that with a "stealth", "assassination" or "thievery" game and I'm sold.