I love healing with my priest, but basically only in raids. I don't enjoy doing anything else on her. Maybe healing is such that if it isn't really challenging, it just isn't much at all. I don't know. Remember how healing heroics was in Wrath? You mostly just stood there. I'm not saying that's what heroics has become in Cata yet, but it's not far from.
I feel the same way. When dpsing, you can always try to get higher dps. With tanking, you can also try to get higher dps, plus you have to deal with marking targets, watching aggro, evaluating a path through the instance, dealing with patrols, and many other things. As a healer, though, once you have it down it's the same thing over and over, in five-mans.
Yet, raiding gets boring much more slowly. Perhaps it's because the fights have something to do even for the healers.
There are ways to improve this situation. One would be for healers to minimize their mana use, thus making a game out of efficient healing the same way dpsers try for higher dps. It would be great to have a mps or hpm meter instead of the usual dps meter.
Another way is to have healers start sneaking in some dps. The main problem I have with this is that, for restoration druids, you run out of mana very quickly unless you spend two points in Fury of Stormrage. However, talent points are hard to come by, so I wouldn't want to do this on a spec that I also use for progression content.
All in all, I feel the pain. I'm not there yet for healing heroics in Cataclysm, but it probably won't be too long before I am.