I have read EJ, Shadowpriest.com, howtopriest, and compared various spriests on wow-heroes, I still haven't found that much consistency on what's the best in slot gear for shadow.
Since I am transitioning from 359 to 372 gear, I see more spriests picking up heroic spirit pieces, and a few rocking the 4 set. So I can't decide if i should use the reg 4piece tier set, or upgrade to heroic non tier pieces.

i.e gear upgrades
Wyrmbreaker's Amulet (Heroic) instead of reg Valiona's Medallion
Crown of the Twilight Queen (Heroic) or Helm of Eldritch Authority (Heroic) instead of the reg Tier Helm
Mantle of Roaring Flames (Heroic) instead of reg Tier shoulders
Bell of Enraging Resonance (Heroic) instead of reg Theralion's Mirror