My undead priest hit level 64 yesterday, and got a new spell: Binding Heal, a spell that heals both me and my target. Situationally useful in groups, useless in solo play. I'll have to see whether I end up using it much, right now I'm not too excited about it. I have 23 talent points in discipline for the improved spirit buff, and now 32 and rising points in holy. Again, useful in groups, but not the easiest spec for soloing.
As a result I'm not making much progress with my quests, still haven't finished all Hellfire quests, but spend most of my time in instances. I'm getting a better feel for what levels and classes are needed for each dungeon. We did the mana tombs with a group with average level of 64, and that was too hard. We managed to kill all bosses in the end, but it took forever, we frequently wiped, and combined with some bad luck in finding boss drops for classes we didn't have, I ended up with a repair bill higher than the worth of the loot. Then I did the slave pens and underbog with two different groups, but both with an average level around 66. And that was simply overkill, which ends up being a lot more fun. Barely any deaths at all, except when we were experimenting with how many mob groups we could pull at once and AoE to death. :) And I got a nice healing cloak, better than my Hide of the Wild I've worn for ages.
I don't think I'll go to Hellfire Ramparts and Blood Furnace any more, at least not at normal difficulty. I think I got all the good priest loot from there, and I stopped gaining reputation from killing the mobs in there. I'm stuck at halfway through honored with Thrallmar and wonder how I'm going to increase that further with the handful of quests I still have. Maybe at heroic difficulty the dungeons give reputation again? I find it a bit annoying to have so many factions and reputation rewards up to exalted dangled before your nose, with no apparent path to reach them.