Now that I have been 85 for a few days and have had the initial shock of healing 5 mans both normal and heroic, I am really starting to enjoy it even more than I thought I would.
Yes, it is hard and intense, but the main problem lies with being confronted with a totally new healing system but at the same time clinging on to how the old system made you feel.
It used to be that mana was hardly an issue (unless you were around with me in the BC era).
Once you start to realize that the mobs that could be CC'd but aren't are the reason we are OOM every pull, you start asking everyone to CC (kick the ones that don't, they need to learn) and mana becomes a thing to always keep an eye on, but is not a life or death thing.
Healers will be the leaders of the CC revolution, not Tanks or Dps.
Previously, our big heals hit like trucks, but that was because the mobs and bosses hit you like a truck and often. With Cata, the goal is NOT to keep everyone at 100% HP 100% of the time. I believe it was quoted a few times from Ghostcrawler and others, that the new system was supposed to feel like Triage. They have given everyone an enormous amount of HP so that we no longer need those huge heals for 60% or more of the players health. The only time even in heroics that I have noticed people take huge spikes of damage has been when CC breaks, or tanks refuse to cc...the spikes in damage come from too many mobs, not the mobs themselves hitting hard.
It took me a few days to get the anxiety of seeing HP bars not at 100% to go away, but once it does.....and you start to make your healing goal be keep everyone alive, and not at 100%....healing in Cata becomes an amazingly fun and interesting activity.
My advice is stick with it...with CC and smart dps and tanks, healing in Cata for a while will be hard....but very rewarding.