It lasts 8 hours with the edge (7 + 0hr) and 6 hours without it for a 33% gain. Considering the length of most protections, 6 is fine to deal with for a low lag/low mana spell. It added no change to dispel I could tell and gave nothing to resistances despite it saying "find they are able to remain in the form of a wraith for longer periods of time, and supposedly to greater effect."

Here's the order of edges at the top. It completely wiped out edges for me for the next 100 hours. A ton of the other options would have been incredibly more valuable. I could have easily taken at least two if not three other edges to benefit.

You can choose the following edges:
Spectral Adept : You may study the lore of Wraiths, to better mimic their insubstantial form.
Master of Decay : You may further study the processes of disease and decay.
Twitchy : Your paranoia and perceptiveness could keep you safe from harm.
Overcome Distortion : You can learn to be resistant to the effects of sensory distortion.
Strong Wrists : Your wrists could be harder than normal to break.
Defensive Withdrawal: You can learn to flee from battle in a more controlled manner, diminishing
opportunities for parting blows.
Hex Augur : You may learn a Hex Augur's awareness of malediction.
Ehren Soul : You can call forth your Ehren Soul and its love of honorable combat.

If you want to keep the insanely high cost for 2 hours, fine, but at least fix the helpfile to point that out. I was expecting a bonus to resistances or at least dispel.

Either way, no one should ever take it imho unless they've got 10+ edges and a god that just hands out immexp like candy.