I recently bought this game - I'm lukewarm with it. I think my perception has been thrown off due to finishing Fallout New Vegas / Dragon Age / Mass Effect 2 just recently - so I'm not in a position to give an opinion without a bias slant to it.
Overall presentation isn't as polished as most modern games and RPG's - especially if you're coming off the 3 I mentioned earlier as a comparison. But it's not bad in any way.
They recently just released a patch to the game so it's more stable now.
The performance of the game has been increased overall since you can now adjust more settings while in-game - so don't worry about that "30 FPS" thing anymore just in case someone mentioned it, since it no longer applies (you can disable any fps cap).
As for fun? Loaded question - I would say you would enjoy it even if you're a casual RPG person. Believe it or not, someone on GameFaqs actually posted a coherent accurate review of the game - so I would read that first if you want another opinion. I on the whole agree with him and his points in general.
http://www.gamefaqs.com/pc/998546-divinity-ii-the-dragon-knight-saga/reviews/review-144417
If you're looking to buy it - Direct2Drive is having a 20% off sale right now (Until Monday - 12/13 I believe) using code HOHOHO (It's on their front page). This makes the game (digital version) down to $32.00 instead of full price.