It's alright. Although not really an open world game I found the settings a fair bit of fun to explore with various hidden treasures and treats hidden everywhere to be found. Combat is... alright. Wouldn't say it's great, but I generally found myself having fun. Fairly well designed as well, with multiple ways to approach most situation and some fun dungeons to plunder. Lots of optional stuff as well. Good diversity with character builds with a good number of talents and skills to choose from and upgrade over time.
Otherwise there are a decent variety of dialogue options and the game doesn't take itself very seriously, which isn't bad. Often things come across as intentionally corny and very tongue-in-cheek which got at least a few chuckles from me. There's crafting of various sorts and later in the game a bit of management with a 'home' you take control over that can be upgraded and such.
Pretty good looking game too, given it's a couple years old now. Soundtrack is nice. Voice acting is mixed however.
Downsides? While the story isn't necessarily bad, the main protagonist is a faceless entity. Not literally faceless, but there's no real personality to your character, which is a shame because the story given a real character to play as could have been a lot more fun. Predictable, but fun. As it is I found it really hard to care about the story because there are no interesting characters to back it. I don't care about my character story-wise, I don't care about any of the NPC. It's kinda lifeless. A little chuckle from some entertaining dialogue is about the best I could hope for from this games NPC.
Like I said before combat isn't bad either, but it's not great either. Just sort of... functional I guess.
Later in the game Divinity 2 mixes it up some by adding a major new mechanic, which is pretty neat, but also introduces some things that will kill you in one hit that aren't very well explained. Actually in general the game doesn't explain itself that well, often leaving it up to the player to figure everything out which can be frustrating at times...
Personally I never beat the game, but I don't regret having bought it either. Can certainly think of better games, among them the first divinity game; Divine Divinity, which was a damned good Diablo style hack & slash. Meanwhile the Gothic series does open world's much better and Arx Fatalis has better dungeon crawling.
Still, can think of much worse too. I know, not the most glowing recommendation. But for what it's worth I had fun with the game.