Well, I have been persevering in the face of bugs, but this one I cannot deal with.

When my heroes got hit by an enchanter, the "Confused" effect did not go away. Given that it's 75% to defense, it pretty much made them useless. This is an amazing mod, and I loved playing it, but it has many bugs that need to be fixed.

Off the top of my head:
On achieving second level, the assassin loses two strength.
More than ten times in a row, killing an enemy mage resulted in him cheating death. Sometimes he appeared right on top of whoever killed him.
The Spellplague counter does not go away even after the caster is eliminated. This disables weave accumulation, and pretty much closes off half the game (including religion) On high difficulty levels, it happens before turn 220.
The "Confused" effect does not go away.
The Musketeers act as clerics.
There is not way to connect cities in the Underdark to cities in the world above.