There are branching dialogs, which can depend on previous quests or events. For the most part NPCs do not react to your appearance. Reputation effects the price of goods you buy/sell/trade, as well as how people treat you (though in most cases there is not a big difference between an NPC having a neutral or positive attitude towards you).
NPCs can react to some changes in the world if they are plot or quest related, but generally not minor stuff like things being moved or stolen. If you are caught stealing NPCs will react (you may be able to talk your way out of it the first couple times) and some NPCs can react strongly to just moving objects or trying to enter certain places (private rooms). It would be good practice to quicksave before trying to steal or pickpocket, in case you get caught (there are ways to avoid a reputation drop from being tossed in jail, but I found it easier to load a previous save if caught).
The world is fairly dynamic, though you can not make large scale changes to the environment (destroy walls, etc). You can create and combine potions, light or put out candles, combine some objects, fill beer mugs, move stuff around, etc. Most beds and bookcases are fixed, but you can pick up or move around chests, barrels, plants, rocks, plates, sacks of grain, bundles of hay, etc.
There are several guilds that you can join, and a couple you can not. There are no mini-games or gambling.
The game is fairly non-linear, except for the very beginning and very end. There are some locations that are only available after certain events or quests, but the game world is fairly open (at some points even a bit overwhelming). You can leave the first village immediately if you wish, and run to places far away where you have no hope of surviving. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
For most of the game I had no problem switching between hack-and-slash (exploring and clearing enemy territory) and non-violent quests or NPC interactions, depending on the mood I was in.
The main plot is about 40-50 hours long. If you explore everywhere and do all the side quests, playtime would be closer to 100 hours. There are about 180 quests that get a quest log entry, though they vary in complexity, some of them are sub-parts of longer quests and some are mutually exclusive (ie you have to choose a side in certain situations).
There are no medium or large scale game changes depending on your actions or character class, so replayability is mostly due to changes in playing style (variations on melee warrior, archer, thief or mage). There are also a lot of easter eggs (references to other games, book characters, etc) and hidden stuff you might not find without help the first time through the game. The main plot quests can be done in different orders, to an extent, but there are no plot branches that would make significant changes when replaying.
