enemies getting tougher, doing greater damage, you take more damage, something like that, but has someone any numbers what exactly happens ?

Difficulty calculates the damage you deal/receive.

Novice
Deal x2
Take x0.5

Apprentice
Deal x1.5
Take x0.75

Adept
Deal x1
Take x1

Expert
Deal x0.75
Take x1.5

Master
Deal x0.5
Take x2

http://www.uesp.net/wiki/Skyrim%3aCombat#Difficulty_Level

Difficulty - Player Damage - Enemy Damage
Novice x2 x0.5
Apprentice x1.5? x0.75
Adept x1 x1
Expert x0.75? x1.5
Master x0.5 x2

It seems like dragons want to get in melee range more often on Master difficulty, and some enemy spellcasters seem to want to kite more and hide behind obstacles, but that's my subjective view.

++ninja

Shame. I was hoping for AI behavior modifications, like increased usage of heals, potions, and changing tactics.

Increasing difficulty by simply changing the damage numbers is a very old and lazy method.

IMO it would feel silly if Beth implemented a bunch of smart AI stuff but didn't put them to use except on higher difficulties.

It would be ridiculous to create really smart AI and only let people who want to play on master experience it.

Most of the time higher difficulty will only mean you take more damage and NPC's take longer to kill.

That means playing on master could make your game even easier -depending on the playstyle -, you level skills like armor, block and melee much faster then on novice.

"Kind of" the reason as to why I set it on Expert. For one, the game is more challenging and I'm constantly dodging, hiding, and using pots or making use of the environment as things don't just die from one sneak arrow... to the knee *har har*.

Also, my skills raise faster (for my progress) due to me using them more than an adept player would.

svcks sometimes though having to turn it down when a bear or saber tooth ambushes me out of nowhere though :/; mind you, that's just so I can back up and fight him; of course, I raise it back up once I catch my bearings

Changing input / output seems like the best method for a sandbox RPG where immersion is a prime aspect - you'd want your NPCs behaving intelligently and convincingly at all times.

With that said, we're a far cry from having immersive behavior. Mr. Bandit, my arrow killing your friend right in-front of you wasn't you just hearing things.

Or in other words : it takes more licks to get to the center of a tootsie pop.

I find it's good to start out on adept difficulty, and then slowly progress your way up. It was kinda surprising, after playing through once on adept, i watched a stream of master difficulty and then everything on adept seemed way too easy >.>

Now I'm playing on expert, and while it seems a bit easy from time to time, I don't think I'm quite ready to upgrade to master just yet. We'll see.

That's one of the things I like about master difficulty. I was going through that first dungeon with the guy that stole the claw (name eludes me right now) on a new character today and things started to go really bad with some Draugrs (3 of them at once) so I ran back to a pressure plate and waited for them and then ran across the plate and let the swinging spike wall kill them. I never found I actually needed to do that on adept, ever. Of course eventually master difficulty gets pretty easy once you've got some levels and decent gear (not even smithed/enchanted gear necessarily), but early on the traps in a dungeon can be as much a help as a hazard.

Also, it really felt like the AI was a bit better on master when I first switched but that might just be because things didn't die in 5 seconds so there was actually time for the AI to do stuff other than run to their death. Like enemies that are low on health sometimes run and hide if they have friends around. Mages actually succeed at casting healing spells because they don't die first. Enemies have time to surround you because the first guy to reach you isn't dead before the second one gets there. Archers dodge in and out of cover to shoot at you when you can't just rush them because you'll die if you try that. Etc...