You can't heal while poisoned and at full health.
Healing with the Heal spell while poisoned gives the message "The cure your poison."
While poisoned, save, heal, and load. You will no longer be poisoned. If you are poisoned and load a game, you will be poisoned. Exiting and opening the game always cures poison. In any case, any poisonous enemy will recharge its single poison shot when you load.
Will and dexterity skills have been switched (you get Iron Will at 5 dexterity, Sniper at 5 will, and so on). The Lockpicking skill can't be used. Sniper has the effect of the Poison skill (+2 damage), and Poison has the effect of Sniper (as far as I can tell).
Magic Unlock can't disable poison fields (poison fields, doors and lightning fields are the only things I've tried so far). It's not very accurate, either (I went through at least 10 uses to get through the two mandatory, otherwise-impassable lightning fields).
Endurance now controls the effect of healing Health and Mana as far as I can tell.
You can Smite and shoot friendly NPCs, even on the overworld. Shooting requires using the attack command on some NPCs, while others are targeted with a right-click.
After defeating The Evil One, you are transported to the special Inaria map. Entering and exiting a dungeon will send you back to the normal Inaria overworld, though the Retreat spell works perfectly, as far as I can tell (After killing The Evil One, Retreat always takes you to the special Inaria overworld. It works even if you don't take the secret passage and immediately Retreat after killing The Evil One).
On the special Inaria overworld, only the king (and the dancing girl) acknowledge you did anything. Also, the dancing girl can't tell when the dance theme has stopped due to you moving around or shopping (she toggles between on and off regardless of the song being played).
Remaining things:
If step switches and attackable switches do anything, I haven't noticed.
Why are there so many dragons around if none of them will ever attack unprovoked?
If you attack an enemy in one of the four far corners of the screen, it will become hostile and stand still as it can't find you. As long as you don't get closer, it will let you shoot it to death.
It looks like you're new here. If you want to get involved, click one of these buttons!