The 2 points in Guardian Totems and 2 in Imp Ghost Wolf make it the PvP spec of choice. The 2 second improved cooldown on Grounding Totem makes a big difference in long arena matches. And the Imp Ghost Wolf I love for chasing down crafty Druids. You think you can Travel Form away from me? HA! Frost Shock + Ghost Wolf and I'm on you. I'll even chase Taurens deep behind enemy lines in AV--I actually get past the usual wall of defense because I'm a bit less conspicuous in Ghost Wolf. That poor druid will be dead before the rest of the horde around him knows whats going on. Getting out is another matter...
Back to the spec. I'm not going to get into the Elemental Devastation debate. You can read all about the myth of that here. I went down that road one week and decided it was garbage. I am however going to point out how important the Nature's Guidance is for raiding as well as Totemic Mastery. Simply put, if you don't have points in Nature's Guidance as an Enhance Shaman you don't belong in a raid.
Prior that spec, I was spec'd 0/44/17 with 5 points in Anticipation being helpful when I did pull aggro (save my butt vs. Gruul a few times) . Also the Improved Reincarnation I considered to be a benefit to the raid. I took Tidal Focus and Healing Focus 3/5 to throw a few Lesser Healing Waves to the MT during some particularly nasty boss fights.
That's actually one of the great things about being a Shaman: so much utility. I can be a chart-topping dps'er and with one eye on the tank can toss in quick heals as back up when say 2 MT healers get Watery Graved in the Tidewalker fight. In fact I specifically keep my MT-Heal macro hotkeyed during that fight. I never used Healing Wave, only Lesser. And being an Enhance Shaman I'm never worried about going OOM. 15 seconds on swings on the boss and I replenish my mana completely.
Now in this spec the Toughness helps across the board against ranged & melee whereas the Anticipation would be a liability against Warriors and less helpful against ranged. Toughness is also unique that it reduces movement slowing effects by 50%, which is of course a huge help to keep from getting kited.
The biggest question for me was should I go 3/3 Mental Quickness and 4/5 Unleashed Rage, or 2/3 MQ & 5/5 UR? I ended up going with the 3/3 & 4/5. I think the extra heal power helps when I have to backup heal our druid and the reduction in shock will help in the final throes of a tight race to eek out one more wicked interrupt despite being so close to OOM that it hurts.