First, the obligatory disclaimer: Anything discussed here is purely analysis on the spells and abilities in their current form. Before Wrath launches these spells could change or be removed entirely. They are not indicative of the final product, just the current, very early stage of it.
John Patricelli of Shifting Perspectives has taken a look at the tanking aspect of things, so I'm going to try to go over the utility the other specs supply.
Restoration gets a smattering of new healing spells of course, all of which are able to be used in Tree of Life as far as we know. There are a few new, interesting mechanics mixed in as well. The ability to regen rage, mana, etc for your party members with your healing spells will make those HoTs of yours even more important than they are now.
A lot of the nagging issues that full Resto Druids haven't been able to shake throughout The Burning Crusade seem to be going the way of Captain Placeholder. A potential direct heal in Tree of Life, as well as another group heal to accompany Tranquility will help Druids keep up with Shaman and Priests in an AOE damage situation.
Feral Druids seem to gain the ability to replicate a couple Warlock curses through their tanking/DPS rotation. At face value, this isn't too incredible in PvE, but it will allow the Warlocks to branch out into other utility(or even DPS) curses. It also seems to be a PvP buff. Again I'll admit my inexperience at PvP, especially with a Druid, but from what I understand, Ferals are in a tough spot in the arena. Their new abilities, while they have PvE applications, are probably a step toward levelling the playing field for them in the arena. Again, for the Druid Tanks out there, you can look toward Johnny P.
Balance seems to fill out their AOE repertoire in Wrath, which was certainly a weak spot of theirs, but beyond that not much seems new. At least, not unique compared to what they had before. This isn't necessarily a bad thing, however. Moonkin aren't necessarily bad right now. What Balance does receive is further pure utility, stepping up the abilities they had before.
I almost positive some of their new utility will be toned down before launch, because it's borderline broken. Things being overpowered in this stage of the game isn't surprising, but wow. I speak of an improvement on Moonkin form. Spell Haste for your party on Spell Crit is an idea I've really liked for a long time, and something I've actually discussed with my guild mates as something that could really help Moonkin or Mage utility. I'm happy to see it implemented in some form, even though it may be gone before long. If not gone, toned down. It's pretty wild currently.
The Balance tree's utility was formerly quite good, but not necessarily targeted very well. It gave benefits to casters, benefits to melee, and benefits to tanks. With the other few changes, it appears that while none of their current utility was nerfed, they've moved away from the widespread utility and have moved towards greater buffs to casters specifically. This might be perceived as a bad thing, and it very well may turn out that way, but I see it as quite good. It increases the direct benefits to their fellow casters and improves their synergy. Some of these things may take Moonkin from something good to have to something essential to the raid, on the level of current day Shadow Priests.
All in all, I think the Druid class will get some good, quality lovin' in Wrath of the Lich King, though maybe not the same kind of loving they have in the Alpha. Better? Worse? It's hard to say, but I think they're at least moving in a good direction. Even if everything currently in the Alpha changes, what does come in Wrath will probably benefit the class all around. It seems that Blizzard has the right idea, and I'm sure they will continue that.
It seems that Shaman and Paladins don't have much (if anything) implemented in the Alpha yet. Because of that, we'll talk about them another day. Until then, I bid you adieu!