I finally beat this today (I bought the game on release but it, along with almost every other single-player game I owned, fell victim to my fixation on Final Fantasy XI). I had a ton of fun and, if this game is true to TDE, I have a lot of respect for German RPG designers :D. The system is just so beautifully crunchy.
I don't have much new to add to everyone else's observations. Combat and encounter design was fantastic. The only thing I would have liked is a little more expansive use of gimmicks, but I never got bored. One thing I struggled with was how the game communicated what was going on to me; I can't tell you how many fights I reloaded simply because I made a mistake that I wouldn't have, if I knew what the fuck was going on. Many's the time I walked over/into gimmicks or traps that were visible but I didn't understand, or got blindsided by AOOs that I didn't think would be triggered etc.
Character development was satisfying for almost 100% of the game, very rare in my experience. It only fell off near the very very very end, and only for non-caster characters. Even in the Temple of the Nameless I was sweating what spells would get APs.
Itemization was also really good for the most part. I particularly enjoyed the massive difference between most of the "end-game" weapons in each category as opposed to their early- and mid-game counterparts. Getting the Andergaster, Pailos, Honorhall's Scepter and Bloodletter felt amazing. I liked that all of the two handers are balanced by having penalties; it's nice to feel like using sword and board, dual wielding and two handed come with real trade-offs. I've also never played a game where I used consumables as much as this one; I loved sniping the shit out of enemies as they closed in with whatever poisons I had to hand. My only real complaint is with armor, I would have appreciated one or two more sets, especially non-metallic (but one more metallic set would've been nice too).
I didn't particularly care that there was no exploration to speak of. Note that I would have cared a lot if there was exploration that was done badly; kudos to Daedalic for focusing their scope and doing really well at what they gave us. However I would have appreciated a strategic layer to the world map, with a fleshed-out camping and travelling system. It would have made provisions feel like something other than cheap megalixirs, for one thing :D.
Lastly, a special shout out to the final Arena fight for being the single most annoying, shitty, retarded encounter in any RPG ever. What the fuck. I don't know who at Daedalic thought it was a good idea to make a fight that consisted solely of whacking away at endless overgrown louses, but whoever it was, they should be dragged into the street by their hair and shot in the public square as a warning to other such degenerates. Even after I figured out exactly the mechanics of the encounter, it was still a boring, maddening, slow-as-molasses grind. I came very close to just quitting the game over it, non-required fight and all; I hated it that much.
In the end I'm glad I stuck with it though. This game was definitely free time well spent.
