MY VERDICT (after my 9 or so hours of playing nonstop) is this:
Graphically, it's beautiful, with weather effects and other small touches (when it rains, each drop makes little ripple pools in water, which is just beautiful, then there's the mist effects, oh man), the score is suitably epic and fantasy-y, which rises in dramatic swells when dragons swoop overhead and what not.
I've not spent much time fiddling with NPCs (too busy stabbing things) and so haven't noticed anything about the Radiant AI, although I will say that the dragon AI is hilariously mean. Sometimes a dragon will ignore you and go right ahead and swoop towards a nearby deer or man or giant and fling them a hundred feet into the air.
Combat feels a bit tighter now, and the various melee 'finishers' that trigger randomly are satisfying (although absent for unarmed attacks MUCH TO MY ANNOYANCE FOREVER ARFGHHFKLSE), and the new spells (fire/lightning/cold stream) are neat. Clairvoyance is actually really useful now.
The mechanics of how your character works are a bit different; attributes are gone. No more Strength or Agility or Speed or Luck. Who you are and how able you are is purely dependent on your skills and gear, and I HATE IT. This means no more tweaking things to be able to outrun deer on foot. For me, it feels like a ton of customization has been ripped away, but I can see how simplifying things makes the game easier to play.
The way leveling works has been changed. Rather than choosing a variety of major and minor skills, as happened in Morrowind and Oblivion, ALL your skills now contribute to leveling, which makes level-ups feel very very very rapid. When you level, you get 1 perk point (which can be spent on stuff like 'one handed weapons now deal 20% more damage' or 'Cast Novice Alteration spells at half-magicka cost'), and can add 10 points either to your Hit Points, Stamina, or Magicka bar.
All together, I feel it works well. I don't like it though, but that's mostly just because I enjoy those niggling little aspects of char-gen/creation.
What really impresses me the most though, is the dungeon design. Caves all feel different, as do the dungeons and the buildings, and it's a treat to go through them and see new-ish stuff every time. Some dungeons have traps and puzzles (no really complex puzzles, but it's still a fun diversion), and all in all, they're vastly improved.
So I'd say 8.75 out of 10. It'd be 9 but they took out all the fun character creation bits I really liked messing with. Also spell creation. >:[
