I can't wait for the new talent trees to kick in with patch 4.0.1. The game designers truly streamlined talent trees, including Enhancement. They've even gone so far as to make Primal Wisdom, our mana regen talent, into a base ability, and they've taken one point out of Unleashed Rage. This frees up two talent points right away and gave us some very viable specs to use right out of the gate of 4.0.1 for our last hurrah at level 80.
I see two different possibilities for level 80 specs for enhancement: Fire Nova or Improved Shields. First, an Improved Fire Nova spec of 5/31/0. Not only did this talent get moved to the enhancement tree, but it got dropped down deep, out of reach for elemental. The unfortunate part is that come Cataclysm, Fire Nova will require a Magma, Fire Elemental or Flametongue Totem and will not work off our new and improved Searing Totem. To further confound matters, the improved nova is right beside Searing Flames, the Searing Totem special kicker.
The improved novas make a big difference in fights requiring both boss and AoE damage, such as heroic Halion-25. Outside of that fight (or any future fights like it), Improved Fire Nova is a waste; better to put the points in Improved Shields. My main spec at 80 will be 5/31/0. Just moving those points isn't going to push your DPS up significantly, but with the changes to Lightning Shield, making it effectively a 10-minute, non-depletable buff (when glyphed), those two points are well spent there at 80.
Dipping into the elemental tree, after our requisite 31 points in enhancement, three points in Acuity are a must-have, especially as we start to level again. The last two points going into Concussion will pack an extra punch.