I would rate this game higher than Baldur's I or II, higher than Diablo, higher even than Torment.
It is expansively free, very non-linear, offers a massive selection of spells and abilities, and the story is just plain fun. If I'd paid $25 or even $30 for it, I would consider it worthwhile. Expect many many many long hours of highly enjoyable fun out of it. It is the RPG version of one of Robert Jordan's Wheel of Time books (if you know what I mean).
But.
This version has serious bugs in it. If you play this, you will often encounter CTD (crash to desktop) - and the worst part is that they can occur in ways that prevent you from accessing entire swaths of territory, or even prevent you from progressing further in the story.
Larian, however, assures us that they will release a patch soon to fix these issues. I am inclined to believe them, as they have sent a representative to gog to liason with customers. However, as it is in its current state, I cannot easily recommend this game to anyone, so three stars only. Once it is patched, this is easily a five or even six star game (if that were possible).
kev