Moonkin Form (or colloquially - Doomkin, Boomkin, Battle Chicken) Is very capable in all aspects that PvP encounters may require. The armor of the chicken makes him reliable whenever the mob you're blasting comes into melee, but without Rage and feral tanking talents (too many to name that make a Bear a good tank) and skills (Swipe, Taunt, etc.), he (the balance druid) is unable to tank in dungeons and raids well enough. That is - in the chicken form he can't tank, while in Bear form he's ability to generate threat is too low to make it sensible.
Balance/Resto spec can make you a reliable healer and a blaster, but all in all, it's something I believe too... shapeless. And GODS this bird is so ugly.
But hey, it might be wise to go Balance at level 40, because you can a) check it out and b) use something a bit more viable at that level, because Feral gets his best toys at levels 50 at best (Mangle) and in 60-ies (Maim, Lacerate, Lifebloom - great when you need to heal between shapeshifts, particularly in PvP when you need a spell cast instantly so it can't be countered)
Edited, Oct 9th 2007 2:33am by XanNerull