In the last 2 games at a high lvl I could jump from roof to roof in the night, hiding there, taking out targets and be off in the night again.
When guards were after me I was able to jump over fences, outrun them and quickly vanish somewhere where they couldn't reach or find me.
Skyrim has completely destroyed my playstile.
I do like the Assassination animations, allthough I can't seem to get any for sleeping targets or when they are sitting, which i find very odd.
Since when is it easier to slit ones throat while he is moving, than sitting still or even sleeping.
However the jumping abilities are just crippled in Skyrim. I can jump higher and further in real life than my well trained Khajit Assassin.
If I ever manage to get on any roof, I just keep sliding down from it. Ok ok the roofs aren't as flat as in morrowind, so what?
I haven't got a flat roof on my own house and can walk on it easily without sliding down.
Also I can ride up nearly every mountain on my horse. When I am on foot however even a 45 degree angle nearly kills me.
Assassins are supposed to be quick, lightfooted, and hard to catch.
Not getting that feeling at all in Skyrim..

I know that probably there wont be anything to change this in Skyrim.
But please consider an Acrobatics Skill tree in your next game.
Give us running, jumping and climbing and the game will get a lot more depth.