The change in difficulty isn't quite as elegant as it is was C1 (at least so far), it seems like guys just kill you faster, but it feels as though I need to use every tool at my disposal to survive every encounter. I'm loving it.
I know people are raggin' on the AI a lot, and I have seen some unfortunate bugs, but for the most part, it's pretty impressive. They'll often leave a guy or two back to provide cover while a few more cautiously move forward to flush me out. Frequently, their point men will approach me from different directions, making stealth kills extremely difficult to perform.
I'll be very interested to see how things continue to shape up as I get further into the game.