Having played the Witcher 2 for a while, I can give you some first impressions....(very) positive, some negative, some neutral
- the graphics are spec-ta-cu-lar. I'm playing the game on high settings with little problems, but medium looks amazing too. It really is a tour de force. In addition to this, loading between areas is almost seamless, giving you the impression you're actually walking around a large town or city. The only thing that annoys me a little is that bloom is sometimes a little overdone, but it can be disabled and in general it's a really small criticism in an otherwise jaw-droppingly gorgeous world.
- conversations and cutscenes are equally polished. Much more convincing than say Mass effect (which isn't a slouch either)
- the atmosphere and character development is top-notch and very convincing. The game, like its predecessor, doesn't shy away from adult themes like moral grey zones, friendships and love and their turmoils and generally racism, violence and sex. It's not a fisherprice good/evil universe. It also surprises you by making you make a few decisions (timer of a few seconds) quickly, or by giving you situations where you can only ask a question or two (as opposed to going down the whole conversation tree). Your priorities will thus shine through in the questiosn you ask, or the topics you want to breach. All this can have small or big consequences down the line.
- You'll have to read the manual to get to the bottom of some things, skills and systems. There's little or no hand-holding, and no real tutorial. At first this irked me a little since I wasn't used to it anymore, but now I'm glad because it makes away with the tedium of a long tutorial.
- The beginning of the game has a few difficulty spikes - since you're not very familiar with the new combat system yet and faced with a few challenging opponents, you get killed a LOT (also because of the no hand-holding as described above). Particularly getting caught in a group of 3-4 opponents is a one way ticket to deathsville, since getting hit in the back does craploads of damage.
The solution is to be patient, use your signs and to roll around a lot. Difficulty gets progressively easier throughout the game, so maybe it's advisable to play the first few hours on easy and then switch to normal to keep things challenging.
Overall, could have been handled better.
- there are a few quick-time events during battles and events. Quite annoying, tbh. One moment you're in the midst of a big battle, the next you're pressing right mouse, filling a mouse click bar or pressing spacebar. Ugh. All in all they're rare, but they are still as ineffective as ever since you can't really watch the (really cool) action on screen as you're frantically waiting for a button to flash down the screen.
- Music is amazing too. So are the menus. Alchemy has been steamlined, making it easier to do (no more ingredients with 3 uses or so, every ingredient has only one puprose now - makes more sense, there are tons of ingredients anyway).
- There have been reports of bugs, but only one small issue for me so far (a small quest that wouldn't end properly, so I took another quest path for it). Technically speaking though, everything has been a-ok. No glitches, crashes, freezes or anything.
- in short, the game is amazing. You should play it asap.
I'll be happy to help out with any questions you have too.
P.S. Satis, another thing to consider on deciding wether to buy Witcher 2 from GOG or Steam may be that Steam possibly offers the censored puritan edition to US players - I'm not sure, but it wouldn't surprise me in the least.