I, for one, like the challenge of Cata healing (I'm a holy priest). It's more difficult, which makes it more lively for me. Healing pre-cata was actually boring to me and most classes could just spam one heal and never go out of mana. Now you actually have to learn to be more mana efficient. Kinda separates the good ones from the pack.
Just my opinion though. I do have mana issues from time to time, but I only ever run out of mana in pick up groups. Never have issues with my own guild groups since everyone knows what they're doing.