Not sure if these are what could properly be called "bugs", but I'll mention them anyway:
-In the base game (I've not yet installed the expansion), I've noticed that townspeople forget that they've ever met my character when I continue from a save. It's a superficial issue, and it's hard to even complain about it "breaking my immersion" when the game just doesn't seem to care about immersing the player in its world in the first place, but still.
-On a related note, any spell effects or persistent special abilities that are active on a character when quitting are forgotten about when reloading. This means if I've just drunk a very expensive stat boost potion (pretty much all of which last for 15 minutes), I can't save and quit for quite a while without wasting the effect. Can be kind of a pain in the ass.
-ALSO, the game doesn't remember whether or not I had the "item text" option toggled on when I continue from a save, and just assumes it was turned on. Extremely minor, but then, it shouldn't have been that difficult to have had the game remember that option like it remembers so many others between sessions.
-There can be numerous "put down the monster uprising" quests on a given dungeon level, but all of them are resolved by killing the exact same monsters. By which I mean: If there are, let's say, five Silt Amorph uprisings that pop up over the course of maybe half an hour, all on the same dungeon level, then when I eventually make it to that level, I can kill however many Silt Amorphs have to be killed to satisfy any one of those five quests (let's say it's three Silt Amorphs which must be killed) and have ALL of those quests completed by killing just the three Amorphs. Some might say, "Hey, free experience! I wouldn't complain," but it's pretty stupid, really. If there are five uprisings with five quests, I should have to kill five sets of monsters to complete all those quests.
Honestly, those are about the only real problems I can think of at the moment, in regard to bugs. For such a low-budget title, it seems pretty polished and bug-free for the most part.