Not at all Thomas! Your clarifications are incredibly useful.
I've played the demo through 3 times, so to address the replay value, I'd say it's pretty good. Depending on your character build and treasure finds, the game does play fairly differently on replays. Combat is different, you may find treasure caches you didn't see before because you lacked Spot Hidden, chests may contain different stuff that can dramatically change your fortunes, that sort of thing.
For example, my Ranger is fairly well-equipped, having decent gear, but my Rogue really lucked out with some treasure finds, obtaining two rings that each gave +5hp and an amulet that gave +5 to hit. So combining that and his sneaky, underhanded skill set really changed the dynamic of the game. Also depending on your Background (ie nationality, human "sub-race") and Axiom (sort of like alignment) you'll get different advantages and abilities which change gameplay.
So, things that impact your character build and his capabilities change, but as pointed out, dialogue and quests do not. So replays are a bit more "mechanical" because that's where you're focusing rather than on the dialogues and atmosphere/setting.
Now I have a question, following Floppymoose's first inquiry - I didn't notice during the demo, but does your class choice actually impact any NPC responses or your reputation during the adventure?
But I guess to add more detail to Thomas' response to #1, at character creation you have 20 points to spend on skills, and your class gives you a free skill that represents your class. Skills cost 3 points to buy and 1 point to increase, so your class essentially gives you 3 free points by providing a skill. So then you can choose to focus on a few skills or diversify with a larger amount of less developed skills. Either way, the free skill from your class is very handy.
There are worlds out there where the sky is burning. And the sea's asleep and the rivers dream … People made of smoke and cities made of song … Somewhere there's danger, somewhere there's injustice, somewhere else the tea's getting cold!