Can't fail on a natural one, no ill effects on a save, magic immunity, spell resistance, mind blank, and freedom of movement on top of that, immune to criticals, 60% chance to block any attack... I haven't exhaustively catalogued stuff. Fast Healing 12, Hardness, Energy Resistance, come back to life once a day, negative effects only last one round... oh, I think I can create a permanent magic circle against evil effect around me or something? Also, all weaponry used against me is effectively nonmagical.
Ah, and I grant a save bonus to allies nearby if my armour and shield is worth more than yours, I think.
... I think, from various sources, I have +16 to all my saves? @_@
Huh, can also walk through a Wall of Force/Prismatic Sphere Thing. Handy.