Ghostform is (IMNSHO) the best 5th level spell available. But it's very hard to adjuctate. A few questions... SRD quotes are from the description of incorporeality. T&B quotes are from the Ghostform spell description.
(My opinions in parentheses.)
"The physical attacks of incorporeal creatures ignore material armor, even magic armor, unless it is made of force or has the ghost touch ability. (SRD)
Ghostform makes you incorporeal. Do attacks (with a Ghost Touch weapon) from a character in Ghostform ignore material armor? (Yes) Do they ignore natural armor? (No)
"Creatures on the Material Plane ignore all your natural armor and natural armor bonuses,[...]" (T&B)
Does this also include Force armor? (No)
"Your touch spells don't work on material targets" (T&B)
Force armor extends onto the ethereal plane, and can "conduct" touch spells. (It is ignored when calculating touch AC.) Can you use touch spells (while in Ghostform) on a target that is using Mage Armor or Bracers of Armor? (?)
"Incorporeal creatures can pass through solid objects at will, although they cannot see when their eyes are within solid matter."
"Incorporeal creatures are inaudible unless they decide to make noise."
"Incorporeal creatures pass through and operate in water as easily as they do in air." (SRD)
Does this mean that characters in Ghostform can cast spells with Verbal components without getting heard on the Material Plane? (?) What if the character is underwater or inside a solid object? (?)
(My opinions in parentheses.)
"The physical attacks of incorporeal creatures ignore material armor, even magic armor, unless it is made of force or has the ghost touch ability. (SRD)
Ghostform makes you incorporeal. Do attacks (with a Ghost Touch weapon) from a character in Ghostform ignore material armor? (Yes) Do they ignore natural armor? (No)
"Creatures on the Material Plane ignore all your natural armor and natural armor bonuses,[...]" (T&B)
Does this also include Force armor? (No)
"Your touch spells don't work on material targets" (T&B)
Force armor extends onto the ethereal plane, and can "conduct" touch spells. (It is ignored when calculating touch AC.) Can you use touch spells (while in Ghostform) on a target that is using Mage Armor or Bracers of Armor? (?)
"Incorporeal creatures can pass through solid objects at will, although they cannot see when their eyes are within solid matter."
"Incorporeal creatures are inaudible unless they decide to make noise."
"Incorporeal creatures pass through and operate in water as easily as they do in air." (SRD)
Does this mean that characters in Ghostform can cast spells with Verbal components without getting heard on the Material Plane? (?) What if the character is underwater or inside a solid object? (?)