Side by Side comparison to it's NQ version provides:
+20 MP
+2% Spell Interruption Rate Down
-5 CHR
+5 MP Recovered while healing
Spell Interruption Rate down is a great macro in piece when casting SS and Blink while soloing in my personal experience. Needless to say this is perfect for casting any enfeebling spells and +20 MP to the NQ Tabard is just cherry on the cake.
This is a macro-in piece for resting MP. It offers +34MP more on mp pool than Errand Houppelande, which is the gear most RDM use to rest.
But if you got Mahatma Houppelande or Yigit Set you should be resting on it. So... it's really useful for those RDM who don't own AFv2 nor those hMP pieces.