It is very fun in BG's. And with the right setup in arena (MS Hunter) you can go Beastcleave and slaughter our opponent with some amazing burst.
We have alot utility in PvP and are best when in groups. We have a nice instant range snare (Frost Shock + Frozen Power) and the pulses of our earthbind totem removes movement impairing debuffs. We must act different on all classes and this takes alot of practice. Like never rush in a Arms Warrior.. your will die.
For PvE there generally isn't more than one in a raid due to other classes being a better DPS choice. Enh shaman do alright on the meters (specifically on tank/spank fights like Saurfang), but if everyone is similarly geared/skilled you should "expect" to be in the lower half of the dps on any movement fight (though in most guilds people aren't of equal gear/skill so it's obviously possible to be higher on the meters).
For PvP we do alright. In arena our single best comp is Beastcleave (enh/bm/hpal) but there are some other comps that I've seen people use (enh/rogue/rdruid, enh/lock/healer, and enh/bm/rdruid (variation of standard beastcleave) are all viable comps if you have good partners). An enh shaman is often best used to disrupt his enemies through various totems, purge, and off-shocking. This means you're playing more of a support role while also DPSing, and that goes for both arena and BGs. If you're undergeared you're going to be even more about support due to having issues with trying to DPS.
Enhance is very fun in Arena and Bg ,
But its harder then other classes and you need skill for it.
Atm im doing arena with an Retridin in 2vs2 @ first it sucked but after some time the engine was running and its going very well now, Btw if you want much HKs go elemental if you want more fun go enhance,
I love enhance and cant wait for cata when Maelstrom also procs lavaburst but it still got an to long CD to be viable in an rotation,