I played for about 4 hours last night, and so far it is living up to the hype, as far as sheer fun to play goes.
Plenty of bugs, including hardcoded keys to WASD settings even if you rebind the keys, you have to use the hardcoded ones for things like lockpicking. Falling through the world, crashes (just 1 in 4 hours), etc.
The graphics do look pretty great with everything at Ultra, although some ugly parts are glaringly obvious, like the water and certain landmasses viewed from high up. High settings are a huge downgrade to quality from Ultra - really bad shadows that crawl around the edges (does this on Ultra every 5 seconds or so also - really strange to watch). Solid 60 FPS from Fraps on High, dipped to 42 occasionally on Ultra. 2600K/8GB/580.
The combat seemed to get an upgrade, and I had a blast fighting other archers (as an archer). Enemies tend to move around more, and fighting seems more tactical, but you can still stand on a tall rock and kill things without worry (problem since Morrowind).
The new character levelling/stats is pretty cool; no more tweaking a level by levelling up skills to get bonuses to stats. Instead you spend points on perks which come available at certain skill levels, so in effect you can have tons of different builds. Liking this so far.
It feels like Oblivion, but enough has been changed or added that it isn't like how New Vegas felt compared to Fallout 3 (the same game).

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