The common wisdom so far is that in 4.0, druids should mainly use regrowth for direct heals, even on targets that already have a regrowth hot. This makes our healing very similar to 3.x except that we use regrowth instead of nourish.
Meanwhile, the Blizzard is trying to change healing more fundamentally. We have mana problems now. We have three direct heals to heal from: small, medium, and large. Nourish, Regrowth, and Healing Touch. The small one is mana efficient, and the medium one is fast, and the big one is efficient but very slow. They all have tradeoffs, so Blizzard hopes we'll be choosing among them.
On fights that aren't demanding, the new conventional wisdom is the way to go. On less demanding fights, you have plenty of mana, and the healing isn't difficult. Just heal like you used to except use regrowth instead of nourish. Do use Thorns. Further, if it gets really boring, remember that you can throw out some dps spells and crowd control now without losing our healing buffs.
I've recently raided on fights that are a bit harder, at least for our group, and the story is a little different. Specifically, we did Algalon (yes, the old Ulduar boss!), and heroic Blood Queen. I'd like to share a few notes about that.
First, on Blood Queen, I had mana problems. I've reforged all my spirit to mastery, under the theory that on fights that are hard, it's usually tank death that is the biggest risk of wiping, not raid member death. Still, my in-combat regen is around 550-600 mp5. It's not enough for the most mana-intensive fights, so I had to tone back on the regrowths and rejuvenates a little. People with a wild growth didn't get a rejuv on top of it, for example. On Algalon, to contrast, mana wasn't as big of a deal. Dps in T10 gear is overkill for this fight, so the fight doesn't really last long enough for mana to be a big issue.
Second, I think healing touch would have been useful on both fights, had I been a pure tank healer. The tanks were taking high damage (something that should change in Cataclysm), but not so high that they would die in three seconds even fully hotted. So if I were in a 25 man and assigned to tank heal, healing touch would have been great. I'd keep up all hots, and cast healing touch as a filler. In a 10 man, though, healing roles aren't as sharply defined. The cast time of healing touch is an eternity if you see a dpser drop below 50%. Thus I mostly used regrowth even on Blood Queen. All I can say is, remember to hit innervate early rather than waiting until you really need it. You want to be hitting innervate early and then at every cooldown.
Third, I really wanted to save swiftmend for the tanks. I'm having a fun time with efflorescence, and on most fights I'm wasting swiftmend so as to place an efflorescence circle somewhere convenient. On both of these harder fights, though, I found that the tanks occasionally dipped below 50%. Swiftmend was much better used for those situations. I would have rather dropped efflorescence in the raid somewhere, typically the melee, but putting it on the tanks is a good second-best.
Finally, our cooldowns add an extra dimension to the play. Tree of life and tranquility are both good things to pop when things get nuts, and it's fun to plan ahead for when that might be. On Blood Queen, the time to use them is after she fears everyone and starts throwing blood bolts. I use tranquility on the first round, and our raid is practically invulnerable. I use tree of life on the second one, and berzerko tree's instant regrowth and improved wild growth really help keep everyone up.