What is the gameplay like in this game? Aside from the combat, skill systems, etc, what is the overall mood? For instance how in Soul Reaver there is a very consistent creepy vibe. Or with the stoic/stiff movement & exploration as Resident Evil 4? Can you jump, is the combat action based in real-time? Or maybe like a bit Darksiders?

Any depth on the overall gameplay experience (say over hours of time) would be awesome. "RPG" means a lot of things these days.

I am playing through the game for the first time right now. I would say it is much closer to Fable than it is to Dragon's Dogma. The setting is medieval, but I wouldn't say the atmosphere is very creepy but it isn't too dopey either (your mileage may vary). You have active control of your character's skill progression, equipment and moderate control over how Geralt interacts with/treats other characters. I am not sure how much your choices affect future events, but it certainly feels like they could. Your save file transfers over to the sequel, so I would imagine your choices do shape the course of the story.

In combat, you have two main weapons (a steel sword for human enemies and a silver sword for supernatural enemies) that each have three different stances (quick, heavy and crowd). You have two secondary weapons/tools (axes, daggers, torches, etc.) and a few spells that you learn as the game progresses. Overall, the combat is a little rigid. The combo system is contingent on precisely timed mouse clicks which I find a little cumbersome when I am being mobbed. Missing the timing will interrupt your attack, thus opening you up to free hits from your enemies. Alas, the difficulty doesn't increase gradually, rather spiking at random times thus forcing you to grind on weaker mobs before you can progress.

The strong point is really the story. The characters and their voice actors help to draw you into the game world and I have really been enjoying the main narrative and many of the side missions as well. Some features, such as the ability to have...relations...with various characters seems a little forced and not very well designed. It doesn't seem to have any affect on the story either, but if you're desperate to see drawings of boobs, this game certainly delivers. The fist-fighting and dice poker mini-games don't affect the story, but they at least offer some nice rewards for completing them.

Overall, I would give the game a 6 out of 10. It's good, but not great. That said, I've heard the second game is vastly improved over this one, so I am really just making my way through this one in order to fully appreciate the sequel. Were I not a completionist and a story junky, I might have given up on this game and jumped straight into Witcher 2.

Well... I would say either Fable or Dragon's Dogma. Why? Because while Fable is fairly tale, Witcher is more folklore based. Heavily. With quite the slavic feel in it (which isn't suprising, considering where the universe of the game was created) - althought it's medieval, it's not so 'knightly'. The royalty are snob assholes, and the peasants are being 'smart', gaining where there can, how they can. Another important, in my opinion, part of the atmosphere is that it ain't shiny. Like I metioned - you will have to deal not only with literal, not sentient monsters, but also with people who deserve to die even more than they do. The whole universe is bitter grey - you try to do something good only to learn you either helped someone bad or you were just been used. I think it's great, but it's my opion, again. :)
And, of course, the whole game is not only dark mood - there is also many happy or just joyfull parts, even relaxing, like Chapter 4. See it for yourself.

Mechanically combat is, mostly, stat based. As in - D&D styled, almost. For example - later on, when you have high enough dexterity you won't get hit and can 'tank' enemies you, earlier, lured to fight one-on-one. Thus - there is no such thing as your 'opening', because attacking doesn't stop enemy, usually, from attacking, unless it's said one-on-one and enemy can be stun-locked. The dificulty is more of a knowledge - to know what attack with what (which style), when and with what potions - especially if you play on higher diffs. This is one of the jolly parts. The game is based on book series and there, too, 'casual' sex was something normal. So you hitting on many woman in game isn't strange, 'lore wise', but it's still your choice. It doesn't really change anything in game. But yes, they went with more mature way with relationships in W2 and 3.

EDIT:
Two things I forgot to mention:
1) Choices do affect the future. Usually after some time, so you have to 'live' with consequences of your decissions.
2) There is no real need to grind in this game, because there are only few spots worth it, and ironically - there are filled with powerful monsters. Instead, you can just do other quests and/or prepare specific potions and oils to help you with a difficult enemy.
Wait until W2, if you plan to play 'Dark Mode' to complain about grinding, belive me. ;P