I'll just chime in on the "disc is good" train.
Two weeks ago, disc was a crappy spec that had to work really hard to achieve 75-80% of a holypriest output, and spending the same mana in doing so, while offering nothing that helped current content raidfights. Now, disc is playing even with monks and gaining mana like it's WoTLK all over again (slight exaggeration).
Holypriest is currently on the bottom of the healing barrel, as tradition dictates, but it isn't by much and I cannot proclaim the spec "bad" or even "comparatively bad". The holy burst is really amazing, HPS is really good. The only limiter of the spec, mana, is manageable even while not overgearing content, though I wouldn't be saying no to it being 10% less tight. But yeah, I'm pretty happy as holy at least. The chakra buffs in 5.1 should put the spec above druids, at the cost of really highlighting how much chakra sucks. I'm honestly more piqued by the long-term prospect of Chakra getting a look-over than anything else from that buff.
As many have said: Different fights need healers with different strengths.
But if you really want the most OP healer out there, look no further than the DK.