One of the things that jumped out at me while writing the Cataclysm version of Shifting Perspectives: Restoration 101 was that Blizzard really did succeed in its effort to make things a little more straightforward for players. While I cut out a few sections that didn't really feel like they were contributing to the discussion of the spec at 85, restoration has fewer caveats these days than it did toward the end of Wrath of the Lich King. Haste in particular is a far smaller rat's nest these days.
As with our other 101 guides, you shouldn't consider this a comprehensive guide; it's a cheat sheet intended to get a player up and running with the spec as quickly as possible. If you're looking for a more encyclopedic approach: http://grousedan.terapad.com/index.cfm?fa=contentGeneric.evzvvgncoennikpo&pageId=2366508
Elitist Jerks' guide to restoration in Cataclysm (updated for patch 4.1) is basically an extended and mathier version of this article.
Restokin's guide to healing at 85 (updated for patch 4.1).
Keeva's (of Tree Bark Jacket) comprehensive restoration druid guide, including tips on leveling, BoA gear, and more. Addresses post-patch 4.1 changes.
Rank 4 Healing Touch's resto healing guide (updated for patch 4.1).
http://www.youfreeweb.com/warlockzk111zhao/
The restoration druid's advantages
Resto druids boast the best array of Heal over Time (HoT) spells in the game.
While we're a little less mobile than we used to be, we're arguably still the most effective healer on the move.
We're able to supply Replenishment to a group/raid.
Our specialized form (the Tree of Life) is available as a 31-point talent that, properly utilized, is a significant efficiency, throughput, and damage boost.
We receive Disentanglement as a passive bonus for speccing into the tree, though I am dying a little inside from the knowledge that this now has to be listed as an "advantage."
We are arguably the most annoying healer to kill in PvP when specced and geared. This tends to be more true as expansions advance, due to how well HoTs pair with increasing resilience.
The spec is generally easy to gear, as there's not much competition for spellpower leather. The only person who'd ever want to roll against you is a moonkin or another resto player, although (as always) you'll still be competing for necklaces, rings, trinkets, and weapons with other healers.
In the wake of patch 4.1 changes, we're probably the healer best placed to compete for top of the meters, if that's something that appeals to you. Hello, 3-minute Tranquility!
While not everyone agrees, I think the new graphic for Tree Form is pretty freaking cool. If you prefer the old version of Tree Form, there's an app glyph for that.
The restoration druid's disadvantages
The druid has limited capacity to address burst damage. Once you've burned Nature's Swiftness and Swiftmend, your only real answer to an unexpected and dangerous damage spike is letting Lifebloom expire (assuming it was on your target in the first place) and/or the extremely inefficient Regrowth.
On that note, Swiftmend's being necessary for Efflorescence is often problematic. You have to choose between using Swiftmend on a target who really needs it or putting Efflorescence where it'll do the most good.
By their very nature, HoTs are more proactive than reactive healing. There are fights where this is a good thing and fights where it's not.
Symbiosis is widely considered the weakest healer mastery.
Fast raid healers are often adept at "sniping" heals before HoTs have a chance to tick, decreasing our effectiveness. Asking other healers to refrain from doing this results in phrases like "screw you" being bandied about.
Restoration druids are the only healing spec with no damage reduction cooldown, an issue that Blizzard's openly acknowledged.
Effective druid healing is dependent on reconfiguring your user interface to show HoT targets and durations. While you can certainly heal without doing this, you're likely to waste a lot of mana.
Less Wow! factor with spells. If you're someone who enjoys seeing an enormous crit heal on a target, you're better off playing another class. Resto druids are about a lot of little numbers, rather than one big one.