Among other characters i got a Druid, a Shaman and a Priest - all 3 are healing spec.
While i am aware that current classes have been balanced for lvl90 (not 85), i am finding Disc to be severely under-performing compared to my other healers.
My Resto Druid has the weakest gear of them all, an average item level of 350.
Surprisingly, my Resto druid is healing so damn well that i am never below 90% mana and even a single HoT+Swiftmend or a Regrowth can bring an ally from 10% to 90% HP.
My Resto Shaman has better gear, an average of ilvl 380.
He is healing with the same awe inspiring results as my poor-geared Druid, holding at around 85-90% mana and handling any AoE healing situation with ease thanks to the new buffed water totems. His single-target spells are so cheap that they give more mana than they cost xD
My Holy/Disc Priest is in ilvl375 gear, with both Holy and Disc as specs.
Holy is performing very well, rarely dropping below 80% mana while easily healing both single and AoE damage. The new "Lightspring" actually is not so bad, while the Divine Hymn is even stronger than before. Chakra "stances" are also easier to use, though i still see no reason why they even exist.
Discipline, on the other hand, is performing very poorly for me - barely hovering around 65% mana.
While it's various shield/absorb spells/procs are doing their job properly, i find them a tad too costly on mana.
However a much bigger issue is with Disc's healing spells being so weak - even after stacking the Grace+Archangel buffs (which takes time and mana), my Disc's Heal/Flash Heal are barely keeping up with the Resto Druid's counterparts.
In other words, even after spending time/mana to stack up Grace/Archangel, my Disc is spending even more mana/time to heal up the same amount of damage my (poorly geared) Resto Druid heals with a fast/cheap Rejuv+Swiftmend or Regrowth.
Where my Holy spec or Druid/Sham could easily AoE heal a party to full with one or two AoE spells, my Disc needs at least 1 or 2 more AoE spells on top of that to heal the same amount of HP.
It also seems that Atonement is vastly weaker than before the MoP patch - my Disc could heal most of the 5man HC trash simply by spamming Smite+Fire, with an occasional heal or a shield; now i find it so weak that it can not handle even mediocre damage.
TL;DR: In short, i find my Disc priest to be performing very poorly - his shielding spells a tad expensive, his healing spells significantly weaker, his Atonement healing is down the drain, his AoE seem to heal for a third less than others, and the Grace/Archangel stacking buffs are annoying.
I used to love healing as Disc before this MoP patch arrived, but if Disc continues performing as it is right now - i do not see myself ever using this spec again.